m68k/mm: enable use of generic memory_model.h for !DISCONTIGMEM

m68k/mm: enable use of generic memory_model.h for !DISCONTIGMEM

The pg_data_map and pg_data_table arrays as well as page_to_pfn() and
pfn_to_page() are required only for DISCONTIGMEM. Other memory models can
use the generic definitions in asm-generic/memory_model.h.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Mike Rapoport <[email protected]>
Cc: Alexey Dobriyan <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Cc: Greg Ungerer <[email protected]>
Cc: John Paul Adrian Glaubitz <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Matt Turner <[email protected]>
Cc: Meelis Roos <[email protected]>
Cc: Michael Schmitz <[email protected]>
Cc: Russell King <[email protected]>
Cc: Tony Luck <[email protected]>
Cc: Vineet Gupta <[email protected]>
Cc: Will Deacon <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>