FIPS: Remove md5-non-fips.c

FIPS: Remove md5-non-fips.c

Commit c9e08af24fd7dda3f21674cdc744579b8c38fa28 removed the only user of
the special case MD5 use that would be allowed in FIPS mode in
tls_prf_sha1_md5(). Commit 271dbf1594bea461ea2ea7946a773a30bfa254aa
removed the file from the build, but left the implementation into the
repository. To clean things up even further, remove this functionality
completely since it is not expected to be needed for FIPS mode anymore.

Signed-hostap: Jouni Malinen <j@w1.fi>