perf genelf: Switch deprecated openssl MD5_* functions to new EVP API

Switch to the flavored EVP API like in test-libcrypto.c, and remove the
bad gcc #pragma.

Inspired-by: 5b245985

 ("tools build: Switch to new openssl API for test-libcrypto")
Signed-off-by: Zixuan Tan <tanzixuan.me@gmail.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/CABwm_eTnARC1GwMD-JF176k8WXU1Z0+H190mvXn61yr369qt6g@mail.gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>