[ARM] S3C64XX: Rename IRQ_UHOST to IRQ_USBH

The USB OHCI host device expects the IRQ definition to be named
IRQ_USBH, so rename the S3C64XX IRQ header to match.

Signed-off-by: Ben Dooks <ben@simtec.co.uk>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>