msm: msm_bus: Fix inconsistent type casting in bandwidth monitor driver

There is a mismatch in size of variable types in different kernel
platform modes like 32bit, 64bit etc. Use proper variable type
in bus bandwidth monitor driver compatible for both platform modes.

Change-Id: Ic69f0eaf6bb02a7b8ef8eae888ddf82ffcc17b26
Signed-off-by: Manaf Meethalavalappu Pallikunhi <manafm@codeaurora.org>