mtl/ofi: add a .gitignore

Ignore generated files.

Signed-off-by: Jeff Squyres <jsquyres@cisco.com>
(cherry picked from commit ac54d771ec7b1805fa96d56b9cbcab5a49e3b8f6)
Signed-off-by: Brian Barrett <bbarrett@amazon.com>

ompi/mca/mtl/ofi/.gitignore

@@ -0,0 +1,5 @@
+mtl_ofi_improbe_opt.c
+mtl_ofi_iprobe_opt.c
+mtl_ofi_irecv_opt.c
+mtl_ofi_isend_opt.c
+mtl_ofi_send_opt.c