leds: st1202: Refactor st1202_led_set() to use !! operator for boolean conversion

leds: st1202: Refactor st1202_led_set() to use !! operator for boolean conversion

st1202_led_set function now uses the !! operator to convert the
enum led_brightness() value to a boolean active state, which is then
passed to the st1202_channel_set() function. This change maintains the
existing functionality.

cocci warnings:
    drivers/leds/leds-st1202.c:194:66-71: WARNING: conversion to bool not needed here.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202502181845.xESVrC61-lkp@intel.com/
Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>
Link: https://lore.kernel.org/r/tencent_3DF7518D407679C99C4CCCB1B8E64638700A@qq.com
Signed-off-by: Lee Jones <lee@kernel.org>