crypto/mem.c: use open-coded aligned alloc when posix_memalign fails

crypto/mem.c: use open-coded aligned alloc when posix_memalign fails

While posix_memalign() is generally not expected to fail, we can always use
the internal aligned alloc implementation to ensure that any
OPENSSL_aligned_malloc failure is indeed fatal and does not require
a fallback.

Signed-off-by: Eugene Syromiatnikov <esyr@openssl.org>
Reviewed-by: Neil Horman <nhorman@openssl.org>
Reviewed-by: Saša Nedvědický <sashan@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/28295)