clk: qcom: clk-rpmh: Fix overflow in BCM vote

Valid frequencies may result in BCM votes that exceed the max HW value.
Set vote ceiling to BCM_TCS_CMD_VOTE_MASK to ensure the votes aren't
truncated, which can result in lower frequencies than desired.

Change-Id: I6d64815ee93c5c604ec0bea86eca00aca570bb9e
Signed-off-by: Mike Tipton <mdtipton@codeaurora.org>