staging: vc04_services: Drop no longer needed headers

Previously, connection.h was only required for the definition of
VCHI_CONNECTION_T, but now all usages of it are gone. Remove this unused
header.

After connection.h is gone, message.h and vchi_cfg_internal.h are no
longer referenced by anything either. Drop them as well.

Signed-off-by: Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
Acked-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>