Various fixes for custom voltage 3
EMIF: implementation of errata i735 for PM timer

EMIF Power Management timer for Self Refresh will put the external SDRAM
in Self Refresh mode after the EMIF is idle for number of DDR clock cycles
that is set with REG_SR_TIM. The minimal value starts at 16 cycles.
However due to Errata i735, the minimal value is 512 DDR cycles as it is
required at OPP100 frequency.
emif: Fix PWR DN value

it's introduced a 0x4 in documentation
Fix for GPU PVR governor, fix for custom voltage