[3.14] gh-144194: Fix mmap failure check in perf_jit_trampoline.c (GH-143713) (#144301)

gh-144194: Fix mmap failure check in perf_jit_trampoline.c (GH-143713)

mmap() returns MAP_FAILED ((void*)-1) on error, not NULL. The current
check never detects mmap failures, so jitdump initialization proceeds
even when the memory mapping fails.
(cherry picked from commit 8fe8a94a7c050bc16cac9ec300f89c0f389f9a44)

Co-authored-by: stratakis <cstratak@redhat.com>