selftests: firmware: fix verify_reqs() return value

commit a6a9be92 ("selftests: firmware: return Kselftest Skip code
for skipped tests") by Shuah modified failures to return the special
error code of $ksft_skip (4). We have a corner case issue where we
*do* want to verify_reqs().

Cc: <stable@vger.kernel.org> # >= 4.18
Fixes: a6a9be92 ("selftests: firmware: return Kselftest Skip code for for skipped tests")
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>