platform: msm: Kconfig: Add bus floor voter feature

Add the bus floor voter feature which allows users the means
to put a floor vote on a bus clock. This change was present
on earlier msm kernels but was accidentally left off during the
move to 3.18 branch.

Change-Id: I1781c836bbfd663d5142f2ebecea3083fceded9b
Signed-off-by: Girish Mahadevan <girishm@codeaurora.org>