ACPI / LPSS: Only call pwm_add_table() for the first PWM controller

At least on the UP board SBC both PWMs are enabled leading to us
trying to add the same pwm_lookup twice, which leads to the following:

[ 0.902224] list_add double add: new=ffffffffb8efd400,
prev=ffffffffb8efd400, next=ffffffffb8eeede0.
[ 0.912466] ------------[ cut here ]------------
[ 0.917624] kernel BUG at lib/list_debug.c:31!
[ 0.922588] invalid opcode: 0000 [#1] SMP
...
[ 1.027450] Call Trace:
[ 1.030185] pwm_add_table+0x4c/0x90
[ 1.034181] bsw_pwm_setup+0x1a/0x20
[ 1.038175] acpi_lpss_create_device+0xfe/0x420
...

This commit fixes this by only calling pwm_add_table() for the first
PWM controller (which is the one used for the backlight).

Link: https://bugzilla.redhat.com/show_bug.cgi?id=1458599
Fixes: bf7696a12071 (acpi: lpss: call pwm_add_table() for BSW...)
Fixes: 04434ab5120a (ACPI / LPSS: Call pwm_add_table() for Bay Trail...)
Signed-off-by: Hans de Goede <[e-mail]>
Acked-by: Andy Shevchenko <[e-mail]>
Cc: 4.11+ <[e-mail]> # 4.11+
Signed-off-by: Rafael J. Wysocki <[e-mail]>

drivers/acpi/acpi_lpss.c

···
 };
 
 struct lpss_private_data {
+	struct acpi_device *adev;
 	void __iomem *mmio_base;
 	resource_size_t mmio_size;
 	unsigned int fixed_clk_rate;
···
 
 static void byt_pwm_setup(struct lpss_private_data *pdata)
 {
+	struct acpi_device *adev = pdata->adev;
+
+	/* Only call pwm_add_table for the first PWM controller */
+	if (!adev->pnp.unique_id || strcmp(adev->pnp.unique_id, "1"))
+		return;
+
 	if (!acpi_dev_present("INT33FD", NULL, -1))
 		pwm_add_table(byt_pwm_lookup, ARRAY_SIZE(byt_pwm_lookup));
 }
···
 
 static void bsw_pwm_setup(struct lpss_private_data *pdata)
 {
+	struct acpi_device *adev = pdata->adev;
+
+	/* Only call pwm_add_table for the first PWM controller */
+	if (!adev->pnp.unique_id || strcmp(adev->pnp.unique_id, "1"))
+		return;
+
 	pwm_add_table(bsw_pwm_lookup, ARRAY_SIZE(bsw_pwm_lookup));
 }
 
···
 		goto err_out;
 	}
 
+	pdata->adev = adev;
 	pdata->dev_desc = dev_desc;
 
 	if (dev_desc->setup)