soc: microchip_mec: Prepare for MEC172x SAF version 2

Microchip MEC172x eSPI SAF has significant hardware changes
requiring a new SAF configuration structure. In preparation
for the MEC172x we move the current SAF header out of common
to the MEC1501 subfolder, remove an unused and empty common
header and remove includes of the moved headers from MEC172x.

Signed-off-by: Jay Vasanth <jay.vasanth@microchip.com>