arm64: tegra: Correct Tegra210 XUSB mailbox interrupt

The XUSB mailbox interrupt for Tegra210 is 40 and not 49 which is for
the XUSB pad controller. For some Tegra210 boards, this is causing USB
connect and disconnect events to go undetected. Fix this by changing the
interrupt number for the XUSB mailbox to 40.

Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>