bus: mhi: core: fix potential operator-precedence with BHI macros

The BHI_MSMHWID and BHI_OEMPKHASH macros take a value 'n' which is
a BHI register index. If 'n' is an expression rather than a simple
value, there can be an operator precedence issue which can result
in the incorrect calculation of the register offset. Adding
parentheses around the macro parameter can prevent such issues.

Signed-off-by: Jeffrey Hugo <jhugo@codeaurora.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Hemant Kumar <hemantk@codeaurora.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>