staging: most: core: rename function

The core module used to have two functions to find a certain
channel. One by name and one by interface. Since no channel is
searched by its interface name anymore the by_name suffix is
rendered redundant. This patch renames the function accordingly.

Signed-off-by: Christian Gromm <christian.gromm@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>