scsi: ufs: continue to boot even with Boot LUN is disabled

scsi: ufs: continue to boot even with Boot LUN is disabled

Several configurable fields of the Device Descriptor and the Unit
Descriptors determine the Boot LUN status. The bBootEnable field and the
bBootLunEn attribute is set to zero by default, so the Boot LUN is
disabled by default.

At which point the scsi device add for Boot LUN will fail, but we can
continue to use the ufs device in fact. This failure shouldn't abort the
device boot.

Signed-off-by: Huanlin Ke <kehuanlin@pinecone.net>
Reviewed-by: Subhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>