test/crypto: replace unsupported with skipped

test/crypto: replace unsupported with skipped

Testcases were previously using -ENOTSUP and TEST_SKIPPED return
statuses interchangeably. Both resulted in the testcase not being run.

These return statuses are now standardised to TEST_SKIPPED.

Signed-off-by: Ciara Power <ciara.power@intel.com>
Acked-by: Declan Doherty <declan.doherty@intel.com>
Acked-by: Hemant Agrawal <hemant.agrawal@nxp.com>
Acked-by: Akhil Goyal <gakhil@marvell.com>
Tested-by: Ruifeng Wang <ruifeng.wang@arm.com>