ftsmc020: move ftsmc020 static mem controller to driver/mtd

Move the header file and definitions of ftsmc020
static memory control unit from a320 SoC folder to
"drivers/mtd" folder.

This change will let other SoC which also use ftsmc020
could share the same header file.

Signed-off-by: Macpaul Lin <macpaul@andestech.com>