clk: qcom: gcc-sdm855: Place a proxy vote on the MMCX rail

On SDM855, due to dependencies on the MMCX rail for turning on
the multimedia AHB clocks and subsequently accessing the display,
camera, and video CC registers, a proxy vote needs to be placed
from the GCC clock driver at probe. This ensures that the
multimedia CC registers are accessible from the respective clock
drivers. At late_initcall_sync, this vote is taken away and the
onus falls on clients to correctly enable their GDSCs or VDD_MMCX
prior to making any clock controller requests.

Change-Id: Ic907cc0ad5adda98ac59a66d8025cfecbc827358
Signed-off-by: Deepak Katragadda <dkatraga@codeaurora.org>