staging: most: move core files out of the staging area

This patch moves the core module to the /drivers/most directory
and makes all necessary changes in order to not break the build.

Signed-off-by: Christian Gromm <christian.gromm@microchip.com>
Link: https://lore.kernel.org/r/1583845362-26707-2-git-send-email-christian.gromm@microchip.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>