[SCSI] ipr: Fix sleeping function called with interrupts disabled

The ata_sas_slave_configure was changed such that it now allocates
some memory for a drain buffer for ATAPI devices. Fixup the ipr
driver such that we no longer make this call with interrupts disabled.

Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>