KVM: arm64: Mark set_sysreg_masks() as inline to avoid build failure

KVM: arm64: Mark set_sysreg_masks() as inline to avoid build failure

When compiling with CONFIG_CC_OPTIMIZE_FOR_SIZE=y, set_sysreg_masks()
fails to compile thanks to:

	BUILD_BUG_ON(!__builtin_constant_p(sr));

as the compiler doesn't identify sr as a constant, despite all the
callers passing constants.

Fix the issue by always inlining this function, which allows GCC to
do the right thing.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202411201857.ZNudtGJl-lkp@intel.com/
Fixes: a0162020095e2 ("KVM: arm64: Extend masking facility to arbitrary registers")
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Link: https://lore.kernel.org/r/20241120111516.304250-1-maz@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>