ffs_aio_cancel() can be called from both interrupt and thread context. Make
sure that the current IRQ state is saved and restored by using
spin_{un,}lock_irq{save,restore}().

Otherwise undefined behavior might occur.
Acked-by: NMichal Nazarewicz <mina86@mina86.com>
Signed-off-by: NLars-Peter Clausen <lars@metafoo.de>
Signed-off-by: NAlexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: NFelipe Balbi <balbi@kernel.org>