IB/qib: Eliminate divide/mod in converting idx to egr buf pointer

The context init now saves a shift from rcvegrbufs_perchunk
rcvegrbufs_perchunk_shift using ilog2.   A BUG_ON() protects the
power of 2 assumption.

Signed-off-by: Mike Marciniszyn <mike.marciniszyn@qlogic.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>
diff --git a/drivers/infiniband/hw/qib/qib.h b/drivers/infiniband/hw/qib/qib.h
index ee993e7..97e6233 100644
--- a/drivers/infiniband/hw/qib/qib.h
+++ b/drivers/infiniband/hw/qib/qib.h
@@ -171,7 +171,9 @@
 	/* how many alloc_pages() chunks in rcvegrbuf_pages */
 	u32 rcvegrbuf_chunks;
 	/* how many egrbufs per chunk */
-	u32 rcvegrbufs_perchunk;
+	u16 rcvegrbufs_perchunk;
+	/* ilog2 of above */
+	u16 rcvegrbufs_perchunk_shift;
 	/* order for rcvegrbuf_pages */
 	size_t rcvegrbuf_size;
 	/* rcvhdrq size (for freeing) */
@@ -940,7 +942,9 @@
 	/* chip address space used by 4k pio buffers */
 	u32 align4k;
 	/* size of each rcvegrbuffer */
-	u32 rcvegrbufsize;
+	u16 rcvegrbufsize;
+	/* log2 of above */
+	u16 rcvegrbufsize_shift;
 	/* localbus width (1, 2,4,8,16,32) from config space  */
 	u32 lbus_width;
 	/* localbus speed in MHz */