Revert "msm: mdss:set brightness to min_bl if brightness is less than min_bl."

Backlight should not be limited to be above a minimum level in the
backlight scale function. Nor should it be limited for all backlight
drivers (should be implemented in the culprit panel's set_backlight func).

This reverts commit 2e5776fd

Change-Id: Idcbf26eb3babb2a29964b9c7fb8e95aa31a8c5b8
Signed-off-by: Carl Vanderlip <carlv@codeaurora.org>