Fix the issue of increasing brightness with KEYCODE_BRIGHTNESS_DOWN event

An issue was identified where the KEYCODE_BRIGHTNESS_DOWN keycode event
would lead to increase in the brightness in the low brightness
conditions. This is happening because we do not constrain the brightness
in a range of 0 to 1 while in the gamma scale.

Bug: 271389272
Test: Manually verified the updated behaviour
Change-Id: I93aea21c621b070b476d6e965970c72ca43b87a7