oak: revise warm reset control for rev3
oak: revise warm reset control for rev3

The AP warm reset pin is changed from rev3 of oak board.
PB3 is stuffed before rev3 and connected to PMIC RESET pin to
reset the AP. For rev3, the AP reset mechanism is changed:
PC3 connects to PMIC SYSRSTB, pull PC3 to low, to reset AP.

BRANCH=none
BUG=none
TEST=manual
1. define CONFIG_BOARD_OAK_REV_2 in board.h
   make -j BOARD=oak
2. define CONFIG_BOARD_OAK_REV_3 in board.h
   make -j BOARD=oak
both cases should be built successfully and run "apreset" command.
AP should be reset normally.

Change-Id: I979e93acf755509f8cb7a12dd77eb7c9e7a98ccc
Signed-off-by: Ben Lok <310171a828df105188e0b545d65d6370e8133283@mediatek.com>
Reviewed-on: https://chromium-review.googlesource.com/289476
Reviewed-by: Rong Chang <3a05493f7adfb36d203f663b3bc2ba30e9d6284f@chromium.org>

fourier49/BIZ_EC,fourier49/BIZ_EC,fourier49/BIZ_EC,fourier49/BIZ_EC