staging: emxx_udc: Change platform dependency to ARCH_RENESAS

Emma Mobile is a Renesas ARM SoC.  Since commit 9b5ba0df ("ARM:
shmobile: Introduce ARCH_RENESAS") is ARCH_RENESAS a more appropriate
platform dependency than the legacy ARCH_SHMOBILE, hence use the
former.

This will allow to drop ARCH_SHMOBILE on ARM in the near future.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>