m68k: Modular Amiga keyboard needs key_maps

| ERROR: "key_maps" [drivers/input/keyboard/amikbd.ko] undefined!

Export key_maps in the Amiga core code, as its defined in an autogenerated
file (drivers/char/defkeymap.c)

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>