[SCSI] mpt fusion: make struct mpt_proc_root_dir static

This patch makes the needlessly global struct mpt_proc_root_dir static.

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Acked-by: "Prakash, Sathya" <Sathya.Prakash@lsi.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>