staging: vc04_services: Remove VCHIQ_SLOT_ZERO_T

Typedefing structs is not encouraged in the kernel.

Signed-off-by: Dominic Braun <inf.braun@fau.de>
Signed-off-by: Tobias Büttner <tobias.buettner@fau.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>