Input: max8997-haptic - fix NULL pointer dereference

NULL pointer derefence happens when booting with DTB because the
platform data for haptic device is not set in supplied data from parent
MFD device.

The MFD device creates only platform data (from Device Tree) for itself,
not for haptic child.

Unable to handle kernel NULL pointer dereference at virtual address 0000009c
pgd = c0004000
[0000009c] *pgd=00000000
Internal error: Oops: 5 [#1] PREEMPT SMP ARM
(max8997_haptic_probe) from [<c03f9cec>] (platform_drv_probe+0x4c/0xb0)
(platform_drv_probe) from [<c03f8440>] (driver_probe_device+0x214/0x2c0)
(driver_probe_device) from [<c03f8598>] (__driver_attach+0xac/0xb0)
(__driver_attach) from [<c03f67ac>] (bus_for_each_dev+0x68/0x9c)
(bus_for_each_dev) from [<c03f7a38>] (bus_add_driver+0x1a0/0x218)
(bus_add_driver) from [<c03f8db0>] (driver_register+0x78/0xf8)
(driver_register) from [<c0101774>] (do_one_initcall+0x90/0x1d8)
(do_one_initcall) from [<c0a00dbc>] (kernel_init_freeable+0x15c/0x1fc)
(kernel_init_freeable) from [<c06bb5b4>] (kernel_init+0x8/0x114)
(kernel_init) from [<c0107938>] (ret_from_fork+0x14/0x3c)

Signed-off-by: Marek Szyprowski <[e-mail]>
Cc: <[e-mail]>
Fixes: 104594b01ce7 ("Input: add driver support for MAX8997-haptic")
[k.kozlowski: Write commit message, add CC-stable]
Signed-off-by: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Dmitry Torokhov <[e-mail]>

drivers/input/misc/max8997_haptic.c

···
 	struct max8997_dev *iodev = dev_get_drvdata(pdev->dev.parent);
 	const struct max8997_platform_data *pdata =
 					dev_get_platdata(iodev->dev);
-	const struct max8997_haptic_platform_data *haptic_pdata =
-					pdata->haptic_pdata;
+	const struct max8997_haptic_platform_data *haptic_pdata = NULL;
 	struct max8997_haptic *chip;
 	struct input_dev *input_dev;
 	int error;
+
+	if (pdata)
+		haptic_pdata = pdata->haptic_pdata;
 
 	if (!haptic_pdata) {
 		dev_err(&pdev->dev, "no haptic platform data\n");