clk: msm: clock: Source the RBCPR clock from active-only XO resource

Use the cxo_clk_src_ao resource to source the HMSS CPR RCG. In
addition, remove it's vote on the CX rail since CX is guaranteed
to be at least SVS2 as long as even one CPU is online.

CRs-Fixed: 983870
Change-Id: I5a4d37310e56235a590e8a93dc8a33d6c3e46e4d
Signed-off-by: Deepak Katragadda <dkatraga@codeaurora.org>