[SCSI] libfc: fix lun reset failure bugs in fc_fcp_resp handling of FCP_RSP_INFO

In LUN RESET testing involving NetApp targets, it is observed that LUN
RESET is failing. The fc_fcp_resp() is not completing the completion
for the LUN RESET task since fc_fcp_resp assumes that the FCP_RSP_INFO
is 8 bytes with the 4 byte reserved field, where in case of NetApp targets
the FCP_RSP to LUN RESET only has 4 bytes of FCP_RSP_INFO. This leads
fc_fcp_resp to error out w/o completing the task completion, eventually
causing LUN RESET to be escalated to host reset, which is not very nice.

Per FCP-3 r04, clause 9.5.15 and Table 23, the FCP_RSP_INFO field can be either
4 bytes or 8 bytes, with the last 4 bytes as "Reserved (if any)". Therefore it
is valid to have 4 bytes FCP_RSP_INFO like some of the NetApp targets behave.
Fixing this by validating the FCP_RSP_INFO against both the two spec allowed
length.

Reported-by: Frank Zhang <frank_1.zhang@intel.com>
Signed-off-by: Yi Zou <yi.zou@intel.com>
Tested-by: Ross Brattain <ross.b.brattain@intel.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>