[SCSI] megaraid_sas: fix EH locking

recent kernels call the eh_ methods without the host lock held.
megaraid_sas doesn't need it but drops it before calling a sleeping
routine and reqcquires it afterwards.  Just remove the
spin_unlock/spin_lock calls.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>