MAINTAINERS: Update m68k Mac entry

MAINTAINERS: Update m68k Mac entry

Two files under drivers/macintosh are actually m68k-only. I think that
patches for these files should be reviewed in the appropriate forum and
merged via the appropriate tree, rather than falling to the powerpc
maintainers to deal with. Update the "M68K ON APPLE MACINTOSH" section
accordingly.

Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Joshua Thompson <funaho@jurai.org>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-m68k@lists.linux-m68k.org
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/fbac2cd8632bb719f48cd1368910abd310548a0e.1607139987.git.fthain@telegraphics.com.au
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>