Revert "mfd: cros_ec: Use devm_kzalloc for private data"

This reverts commit 3aa2177e47878f7e7616da8a2050c44f22301b6e.

That commit triggered a new WARN when unloading the module (see at the
end of the commit message). When a class_dev is embedded in a structure
then that class_dev is the thing that controls the lifetime of that
structure, for that reason device managed allocations can't be used here.
See Documentation/kobject.txt.

Revert the above patch, so the struct is allocated using kzalloc and we
have a release function for it that frees the allocated memory, otherwise
it is broken.

------------[ cut here ]------------
Device 'cros_ec' does not have a release() function, it is broken and must be fixed.
WARNING: CPU: 3 PID: 3675 at drivers/base/core.c:895 device_release+0x80/0x90
Modules linked in: btusb btrtl btintel btbcm bluetooth ...
CPU: 3 PID: 3675 Comm: rmmod Not tainted 4.20.0-rc4 #76
Hardware name: Google Kevin (DT)
pstate: 40000005 (nZcv daif -PAN -UAO)
pc : device_release+0x80/0x90
lr : device_release+0x80/0x90
sp : ffff00000c47bc70
x29: ffff00000c47bc70 x28: ffff8000e86b0d40
x27: 0000000000000000 x26: 0000000000000000
x25: 0000000056000000 x24: 0000000000000015
x23: ffff8000f0bbf860 x22: ffff000000d320a0
x21: ffff8000ee93e100 x20: ffff8000ed931428
x19: ffff8000ed931418 x18: 0000000000000020
x17: 0000000000000000 x16: 0000000000000000
x15: 0000000000000400 x14: 0000000000000143
x13: 0000000000000000 x12: 0000000000000400
x11: 0000000000000157 x10: 0000000000000960
x9 : ffff00000c47b9b0 x8 : ffff8000e86b1700
x7 : 0000000000000000 x6 : ffff8000f7d520b8
x5 : ffff8000f7d520b8 x4 : 0000000000000000
x3 : ffff8000f7d58e68 x2 : ffff8000e86b0d40
x1 : 37d859939c964800 x0 : 0000000000000000
Call trace:
device_release+0x80/0x90
kobject_put+0x74/0xe8
device_unregister+0x20/0x30
ec_device_remove+0x34/0x48 [cros_ec_dev]
platform_drv_remove+0x28/0x48
device_release_driver_internal+0x1a8/0x240
driver_detach+0x40/0x80
bus_remove_driver+0x54/0xa8
driver_unregister+0x2c/0x58
platform_driver_unregister+0x10/0x18
cros_ec_dev_exit+0x1c/0x2d8 [cros_ec_dev]
__arm64_sys_delete_module+0x16c/0x1f8
el0_svc_common+0x84/0xd8
el0_svc_handler+0x2c/0x80
el0_svc+0x8/0xc
---[ end trace a57c4625f3c60ae8 ]---

Cc: [e-mail]
Fixes: 3aa2177e4787 ("mfd: cros_ec: Use devm_kzalloc for private data")
Signed-off-by: Enric Balletbo i Serra <[e-mail]>
Reviewed-by: Guenter Roeck <[e-mail]>
Reviewed-by: Dmitry Torokhov <[e-mail]>
Signed-off-by: Lee Jones <[e-mail]>

drivers/mfd/cros_ec_dev.c

···
 #endif
 };
 
+static void cros_ec_class_release(struct device *dev)
+{
+	kfree(to_cros_ec_dev(dev));
+}
+
 static void cros_ec_sensors_register(struct cros_ec_dev *ec)
 {
 	/*
···
 	int retval = -ENOMEM;
 	struct device *dev = &pdev->dev;
 	struct cros_ec_platform *ec_platform = dev_get_platdata(dev);
-	struct cros_ec_dev *ec = devm_kzalloc(dev, sizeof(*ec), GFP_KERNEL);
+	struct cros_ec_dev *ec = kzalloc(sizeof(*ec), GFP_KERNEL);
 
 	if (!ec)
 		return retval;
···
 	ec->class_dev.devt = MKDEV(ec_major, pdev->id);
 	ec->class_dev.class = &cros_class;
 	ec->class_dev.parent = dev;
+	ec->class_dev.release = cros_ec_class_release;
 
 	retval = dev_set_name(&ec->class_dev, "%s", ec_platform->ec_name);
 	if (retval) {