qla4xxx: Fix sparse warning

qla4xxx: Fix sparse warning

Fix following warning:-
drivers/scsi/qla4xxx/ql4_os.c:35:5: warning: symbol 'ql4xdisablesysfsboot' was not declared. Should it be static?

drivers/scsi/qla4xxx/ql4_iocb.c:461:5: warning: symbol 'qla4xxx_send_mbox_iocb' was not declared. Should it be static?

drivers/scsi/qla4xxx/ql4_os.c:3025:6: warning: symbol 'qla4xxx_do_work' was not declared. Should it be static?

Signed-off-by: Vikas Chaudhary <vikas.chaudhary@qlogic.com>