If bootloader doesn't terminate its last spi operation properly
before starting kernel, our first transfer in kernel becomes a
continuous transfer to that request instead of a new one.
Fix this flaw by restoring IOC register, which restored all pin
state to default.
Fixes: ebf0d8dade ("ath79: add new ar934x spi driver")
Reported-by: Russell Senior <russell@personaltelco.net>
Signed-off-by: Chuanhong Guo <gch981213@gmail.com>
