[SCSI] megaraid: fix section mismatch

Change megaraid_pci_driver_g variable name so that it matches the modpost
whitelist that allows pointers to init text/data.

WARNING: vmlinux.o(.data+0x1a8e30): Section mismatch: reference to .init.text:megaraid_probe_one (between 'megaraid_pci_driver_g' and 'class_device_attr_megaraid_mbox_app_hndl')

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>