clk: msm: clock-gcc-8996: Mark XO as bimc_clk parent

Make CXO as bimc_clk's parent so that XO shutdown does
not happen if there is still a DDR sleep vote.

Change-Id: I67ea5f845d33f903fd5b66ddaa766c3c608e8ce0
Signed-off-by: Deepak Katragadda <dkatraga@codeaurora.org>