arm64: micro-bench: ioremap userspace_emulated_addr

We should explicitly ioremap the userspace emulated address used
in the benchmark.

Reported-by: Alexandru Elisei <alexandru.elisei@arm.com>
Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Tested-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Andrew Jones <drjones@redhat.com>