[SCSI] qla2xxx: fix to honor ignored parameters in sysfs attributes

This is a patch to fix 'segmentation fault' issue which was initiated
by Richard Lary <rlary@us.ibm.com>.  Thanks again Richard.

- on following sysfs attritute function, changes have made so that both
  count and offset input parameters are honored by the functions.
    = qla2x00_sysfs_read_nvram()
    = qla2x00_sysfs_read_vpd()
- made changes so that NVRAM data to be cached to minimize H/W accesses
  during agent querying of the driver's.

Signed-off-by: Seokmann Ju <seokmann.ju@qlogic.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>