USB: EHCI: fix divide-by-zero bug

This patch (as1164) fixes a bug in the EHCI scheduler.  The interval
value it uses is already in linear format, not logarithmically coded.
The existing code can sometimes crash the system by trying to divide
by zero.
Signed-off-by: NAlan Stern <stern@rowland.harvard.edu>
Cc: David Brownell <david-b@pacbell.net>
Cc: Stable <stable@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/usb/host/ehci-sched.c

@@ -918,7 +918,7 @@ iso_stream_init (
 		 */
 		stream->usecs = HS_USECS_ISO (maxp);
 		bandwidth = stream->usecs * 8;
-		bandwidth /= 1 << (interval - 1);
+		bandwidth /= interval;
 
 	} else {
 		u32		addr;
@@ -951,7 +951,7 @@ iso_stream_init (
 		} else
 			stream->raw_mask = smask_out [hs_transfers - 1];
 		bandwidth = stream->usecs + stream->c_usecs;
-		bandwidth /= 1 << (interval + 2);
+		bandwidth /= interval << 3;
 
 		/* stream->splits gets created from raw_mask later */
 		stream->address = cpu_to_hc32(ehci, addr);