perf/smmuv3: Don't cast parameter in bit operations

While in this particular case it would not be a (critical) issue,
the pattern itself is bad and error prone in case somebody blindly
copies to their code.

Don't cast parameter to unsigned long pointer in the bit operations.
Instead copy to a local variable on stack of a proper type and use.

Note, new compilers might warn on this line for potential outbound access.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/20220209184758.56578-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Will Deacon <will@kernel.org>