mediatek/mt8173: add APLL clock setting

Add a new function mt_pll_set_aud_div() to set APLL for audio I2S.
The function is called by mainboard's configure_audio().

BRANCH=chromeos-2015.07
BUG=chrome-os-partner:41507
TEST=build and verified pass on oak board

Change-Id: Ia3c2f250627028422a7427b93d78d49545eb7a75
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: bb18943f5e74af7723bd4e01d4da96c0b153a0f6
Original-Change-Id: I7996a8048f2e54ab09093cca3c8bc7447b61170f
Original-Signed-off-by: Koro Chen <koro.chen@mediatek.com>
Original-Reviewed-on: https://chromium-review.googlesource.com/297225
Original-Commit-Ready: Yidi Lin <yidi.lin@mediatek.com>
Original-Tested-by: Yidi Lin <yidi.lin@mediatek.com>
Original-Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/13090
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>
2 files changed