platform_get_irq() returns a negative number on failure, so adjust the
logic to detect such condition and propagate the real error value on
failure.
Signed-off-by: NFabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Cc: Ley Foon Tan <lftan@altera.com>