Add ISP24xx flash-manipulation routines.

Add read/write flash manipulation routines for the ISP24xx.
Update sysfs NVRAM objects to use generalized accessor
functions.
Signed-off-by: NAndrew Vasquez <andrew.vasquez@qlogic.com>
Signed-off-by: NJames Bottomley <James.Bottomley@SteelEye.com>