oshmem: fix warnings

fixed by Igor, reviewed by Miked

cmr=v1.8.2:reviewer=ompi-rm1.8

This commit was SVN r32217.

oshmem/mca/memheap/memheap.h

@@ -159,7 +159,7 @@ OSHMEM_DECLSPEC extern mca_memheap_base_module_t mca_memheap;
  */
 static inline int mca_memheap_base_can_local_copy(sshmem_mkey_t *mkey, void *dst_addr) {
     return mca_memheap.memheap_is_symmetric_addr(dst_addr) &&
-        0 == mkey->len && MAP_SEGMENT_SHM_INVALID != mkey->u.key; 
+        (0 == mkey->len) && (MAP_SEGMENT_SHM_INVALID != (int)mkey->u.key);
 }