video: backlight: sky81452-backlight: Fix some kerneldoc issues

Firstly, all lines must begin with a '*'.  Secondly, arg descriptions
must be spelt correctly, so fix misspelling of 'gpioD_enable' and
'short_detecTion_threshold'

Fixes the following W=1 kernel build warning(s):

 drivers/video/backlight/sky81452-backlight.c:46: warning: bad line:                 If it is not defined, default name is lcd-backlight.
 drivers/video/backlight/sky81452-backlight.c:64: warning: Function parameter or member 'gpiod_enable' not described in 'sky81452_bl_platform_data'
 drivers/video/backlight/sky81452-backlight.c:64: warning: Function parameter or member 'short_detection_threshold' not described in 'sky81452_bl_platform_data'

Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>