staging: fsl-mc: return -EINVAL for all fsl_mc_portal_allocate() failures

There are some error paths that allow for a NULL new_mc_io and err = 0
return code. Return -EINVAL instead.

Signed-off-by: Horia Geantă <horia.geanta@nxp.com>
Signed-off-by: Stuart Yoder <stuart.yoder@nxp.com>
Acked-by: German Rivera <german.rivera@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>