fix(deck): Add udev rule for Galileo brightness control

Author: KyleGospo

system_files/deck/shared/usr/lib/udev/rules.d/30-steamdeck.rules

@@ -1,6 +1,8 @@
 # Enables brightness slider in Steam
 # - /sys/class/backlight/amdgpu_bl0/brightness
+# - /sys/devices/platform/AMDI0010:02/i2c-2/i2c-ANX7580A:00/{brightness,bmode}
 ACTION=="add", SUBSYSTEM=="backlight", KERNEL=="amdgpu_bl0", RUN+="/usr/bin/chmod a+w /sys/class/backlight/%k/brightness"
+ACTION=="add", SUBSYSTEM=="i2c", KERNEL=="i2c-ANX7580A:00", RUN+="/usr/bin/chmod a+w /sys/%p/brightness /sys/%p/bmode"
 
 # Enables manual GPU clock control in Steam
 # - /sys/class/drm/card0/device/power_dpm_force_performance_level