staging: most: replace MOST_CH_ISOC_AVP with MOST_CH_ISOC

This patch replaces the enum value MOST_CH_ISOC_AVP with the more
appropriate MOST_CH_ISOC.

Signed-off-by: Andrey Shvetsov <andrey.shvetsov@k2l.de>
Signed-off-by: Christian Gromm <christian.gromm@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>