backlight: lp855x: Fix lp855x.h kernel-doc warnings

Add a missing struct short description and a missing leading " *" to
lp855x.h to avoid kernel-doc warnings:

Warning: include/linux/platform_data/lp855x.h:126 missing initial short
 description on line:
 * struct lp855x_platform_data
Warning: include/linux/platform_data/lp855x.h:131 bad line:
   Only valid when mode is PWM_BASED.

Fixes: 7be865a ("backlight: new backlight driver for LP855x devices")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Daniel Thompson (RISCstar) <danielt@kernel.org>
Link: https://patch.msgid.link/20251111060916.1995920-1-rdunlap@infradead.org
Signed-off-by: Lee Jones <lee@kernel.org>

Author: rddunlap

include/linux/platform_data/lp855x.h

@@ -124,12 +124,12 @@ struct lp855x_rom_data {
 };
 
 /**
- * struct lp855x_platform_data
+ * struct lp855x_platform_data - lp855 platform-specific data
  * @name : Backlight driver name. If it is not defined, default name is set.
  * @device_control : value of DEVICE CONTROL register
  * @initial_brightness : initial value of backlight brightness
  * @period_ns : platform specific pwm period value. unit is nano.
-		Only valid when mode is PWM_BASED.
+ *		Only valid when mode is PWM_BASED.
  * @size_program : total size of lp855x_rom_data
  * @rom_data : list of new eeprom/eprom registers
  */