[SCSI] qla2xxx: Correct maximum supported lun and target-id definitions.

Correct maximum supported lun and target-id definitions.

The driver uses command-IOCBs which support a maximum lun
value of 0xffff -- correct #define to reflect the change.
Also, remove superfluous MAX_TARGET definition.

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