staging: vchi: Use vchiq's enum vchiq_reason

enum vchi_callback_reason maps 1:1 to enum vchiq_reason, in an effort to
simplify things, let's use the later, and get rid of the extra
indirection.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Link: https://lore.kernel.org/r/20200629150945.10720-21-nsaenzjulienne@suse.de


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>