IB/qib: Add missing <linux/slab.h> include

Fix build failure on sparc64 which is missing the include of
<linux/slab.h> via <asm/pci.h> that x86, powerpc, ia64, etc. have.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NRoland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/qib/qib.h

@@ -45,6 +45,7 @@
 #include <linux/mutex.h>
 #include <linux/list.h>
 #include <linux/scatterlist.h>
+#include <linux/slab.h>
 #include <linux/io.h>
 #include <linux/fs.h>
 #include <linux/completion.h>