clk: msm: clock-osm: fix read-modify-write for LLM volt vote register

Currently, LLM_INTF_DCVS_DISABLE register is written values
directly instead of doing a read-modify-write. Fix this.

CRs-Fixed: 1101488
Change-Id: I1f99dc4b37e809cdc6fb4cafe7fb0b6d585cbd76
Signed-off-by: Osvaldo Banuelos <osvaldob@codeaurora.org>