staging: vc04_services: Remove extern variable

This patch removes extern variable vchiq_arm_log_level, because it is
already declared in vchiq_arm.h

Issue found by checkpatch.pl

Signed-off-by: Mihaela Muraru <mihaela.muraru21@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>