Rename div64_64 to div64_u64 to make it consistent with the other divide
functions, so it clearly includes the type of the divide. Move its definition
to math64.h as currently no architecture overrides the generic implementation.
They can still override it of course, but the duplicated declarations are
avoided.

Signed-off-by: Roman Zippel
Cc: Avi Kivity
Cc: Russell King
Cc: Geert Uytterhoeven
Cc: Ralf Baechle
Cc: David Howells
Cc: Jeff Dike
Cc: Ingo Molnar
Cc: "David S. Miller"
Cc: Patrick McHardy
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds