at91: Backport determine_rate prototype fix

at91: Backport determine_rate prototype fix

This patch is backport of a fix to a USB prototype mismatch bug found
in 3.18 kernels, originally submitted by Boris Brezillon [1].
The symptom of this bug was that devices attached to the at91 using
at91_ohci on a hub never appeared and failed to initialise.

[1] http://www.spinics.net/lists/linux-usb/msg125969.html

Signed-off-by: Ben Whitten <ben.whitten@gmail.com>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@46649 3c298f89-4303-0410-b956-a3cf2f4a3e73