IB/qib: Make qib_driver static

struct pci_driver qib_driver is only used in qib_init.c.  Remove it
from qib.h and make it static in qib_init.c.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Roland Dreier <roland@purestorage.com>