selftests/arm64: Check failures to set tags in check_tags_inclusion

The MTE check_tags_inclusion test uses the mte_switch_mode() helper but
ignores the return values it generates meaning we might not be testing
the things we're trying to test, fail the test if it reports an error.
The helper will log any errors it returns.

Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>
Link: https://lore.kernel.org/r/20220510164520.768783-4-broonie@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>