platform: msm: qcom-geni-se: Fix the race condition during bus voting

When two bus votes are added, one of them is executed while the second one
performs nothing. But the thread that does the second vote continues and
accesses the yet-to-be-clocked registers while the thread that does the
first vote is working on the votes to be executed. This leads to unclocked
register access.

Replace the spin_lock that protects the bus voting logic with a mutex and
protect the entire bus voting logic with that lock.

CRs-Fixed: 2093107
Change-Id: I1852566891d507f5599c4227ff7655e2bfc84598
Signed-off-by: Karthikeyan Ramasubramanian <kramasub@codeaurora.org>