libmemunreachable: turn off MEM_ALOGV messages

The move to async safe logging in I3d3b2111f6f6bf8a0d7039295d34d5168c191651
caused MEM_ALOGV messages to print even when NDEBUG was set.

Test: builds
Change-Id: Ibebe69d8c96f8f2556991c1eb5446a77782d43c7
1 file changed