rpmsg: Correct support for MODULE_DEVICE_TABLE()

Due to missing a missing entry in file2alias.c MODULE_DEVICE_TABLE() are
not generating the proper module aliases. Add the needed entry here.

Fixes: bcabbcca ("rpmsg: add virtio-based remote processor messaging bus")
Reported-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Andrew F. Davis <afd@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>