[SCSI] ipr: add MMIO write to perform BIST for 64 bit adapters

The 64 bit chip used in new adapters does not properly support the BIST register
in PCI config space.  This patch implements an alternative MMIO write reset
method.

Signed-off-by: Wayne Boyer <wayneb@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>