aha1542: rework locking

Remove aha1542_lock and use host_lock instead.
Remove interrupt and queuecommand function wrappers.
Remove locking from lowlevel _out and _in functions, they now can
onle be called (at runtime) with host_lock being held.
Remove ssleep(4) in aha1542_reset as we can't sleep while holding a spinlock.
It's useless anyway as wait_mask will wait until the controller is idle and
kernel waits for 10 seconds (HOST_RESET_SETTLE_TIME) after that.
Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: James Bottomley <JBottomley@Odin.com>