After the commit 8938b449137f1db8755154c37d87a19dfbebc526 were we removed
duplicated value of gpu... we have again to downclock the gpu setting its
initial value to 200Mhz (commit 389054c60118e03ce36e6abddb495273eb9adf36)
backlight: use exponential backlight control instead of linear.

Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>