platform_get_irq() can return negative error values and we already test for
these. Therefore the variable holding this value should be signed to not
loose possible error values.
Reported-by: NDavid Binderman <dcb314@hotmail.com>
Signed-off-by: NHeiko Stuebner <heiko@sntech.de>
Reviewed-By: NDaniel Kurtz <djkurtz@chromium.org>