kernel.h: unconditionally include asm/div64.h for do_div()

Include asm/div64.h for do_div() usage in DIV_ROUND_DOWN_ULL() and
DIV_ROUND_CLOSEST_ULL().  Remove the old CONFIG_LBDAF=y conditional
include.

Link: http://lkml.kernel.org/r/20181228153430.23763-1-jani.nikula@intel.com


Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>