The spinlock is held over too large a region: pscratch is a permanent
address (it's allocated at boot time and never changes).  All you need
the smp lock for is mediating the scratch in use flag, so fix this by
moving the spinlock into the case where we set the pscratch_busy flag
to false.

Cc: Stable Tree <stable@kernel.org>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>