[SCSI] qla2xxx: Add Flash Layout Table support.

The Flash Layout Table (FLT) present on many recent HBAs encodes
flash usage information, organizes data stored into separate
regions and presents the information uniformly to the driver.
Use this information rather than using specific hard-coded values
based on ISP type.

Signed-off-by: Andrew Vasquez <andrew.vasquez@qlogic.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>