kselftest/arm64: Use ksft_perror() to log MTE failures

kselftest/arm64: Use ksft_perror() to log MTE failures

The logging in the allocation helpers variously uses ksft_print_msg() with
very intermittent logging of errno and perror() (which won't produce KTAP
conformant output) when logging the result of API calls that set errno.
Standardise on using the ksft_perror() helper in these cases so that more
information is available should the tests fail.

Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Link: https://lore.kernel.org/r/20241029-arm64-mte-test-logging-v1-1-a128e732e36e@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>