staging: vchiq_core: Replace remaining BUG_ON with WARN_ON

This replaces all remaining BUG_ON with WARN_ON. So in case of
a VCHIQ bug the system is still usable.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>