scsi: ufs: don't try adding boot and rpmb lun if not supported

UFS devices can support upto 4 well known logical units: "REPORT_LUNS",
"UFS Device", "RPMB" & "BOOT".

"REPORT_LUNS" & "UFS Device" are mandatory for all device classes
("bDeviceSubClass" parameter of device descriptor) while "BOOT" is
supported only for bootable devices. "RPMB" is only supported with
embedded devices.

This function tries to add scsi device instances for each of all well
known LUs (except "REPORT LUNS" LU) if it is advertised to be supported
by device class.

Change-Id: Iec26abba64be4bf790e3d19e4335ed820494b646
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>