HID: amd_sfh: Add illuminance mask to limit ALS max value

ALS illuminance value present only in first 15 bits from SFH firmware
for V2 platforms. Hence added a mask of 15 bit to limit ALS max
illuminance values to get correct illuminance value.

Fixes: 0aad9c95

 ("HID: amd_sfh: Extend ALS support for newer AMD platform")
Signed-off-by: Basavaraj Natikar <Basavaraj.Natikar@amd.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>