Refactor PLL code which will be reused among similar SOCs.
BUG=b:80501386
BRANCH=none
TEST=Boots correctly on Elm
Change-Id: I11f044fbef93d4f5f4388368c510958d2b0ae66c
Signed-off-by: Tristan Shieh <tristan.shieh@mediatek.com>
Reviewed-on: https://review.coreboot.org/27305
Reviewed-by: Julius Werner <jwerner@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>