Fix shm_open posix compliance error code
Handle EISDIR in shm_open like glibc does, and set EINVAL.
* librt/shm.c (shm_open): Handle EISDIR error.
Signed-off-by: Mickaël Guêné <mickael.guene@st.com>
Signed-off-by: Christophe Lyon <christophe.lyon@st.com>