Make lpm display mode follow the brightness setting in manual mode

Previously minimum brightness was used for lpm brightness unless
automatic mode was enabled. Now it follows the display brightness
setting in manual mode.

[mce] Make lpm display mode follow the brightness setting in manual mode. Fixes JB#20227
Merge pull request #178 from spiiroin/lpm_manual_brightness

Make lpm display mode follow the brightness setting in manual mode