kernel.h: implement DIV_ROUND_CLOSEST_ULL

kernel.h: implement DIV_ROUND_CLOSEST_ULL

We have grown a number of different implementations of
DIV_ROUND_CLOSEST_ULL throughout the kernel.  Move the i915 one to
kernel.h so that it can be reused.

Signed-off-by: Javi Merino <[email protected]>
Reviewed-by: Jeff Epler <[email protected]>
Cc: Jani Nikula <[email protected]>
Cc: David Airlie <[email protected]>
Cc: Guenter Roeck <[email protected]>
Acked-by: Daniel Vetter <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: Alex Elder <[email protected]>
Cc: Antti Palosaari <[email protected]>
Cc: Javi Merino <[email protected]>
Cc: Mauro Carvalho Chehab <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Mike Turquette <[email protected]>
Cc: Stephen Boyd <[email protected]>
Cc: Stephen Hemminger <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>