bitops: Move find_next_bit.o from lib-y to obj-y

If there are no builtin users of find_next_bit_le() and
find_next_zero_bit_le(), these functions are not present in the kernel
image, causing m68k allmodconfig to fail with:

  ERROR: "find_next_zero_bit_le" [fs/ufs/ufs.ko] undefined!
  ERROR: "find_next_bit_le" [fs/udf/udf.ko] undefined!
  ...

This started to happen after commit 171d809d ("m68k: merge mmu and
non-mmu bitops.h"), as m68k had its own inline versions before.

commit 63e424c8 ("arch: remove CONFIG_GENERIC_FIND_{NEXT_BIT,
BIT_LE, LAST_BIT}") added find_last_bit.o to obj-y (so it's always
included), but find_next_bit.o to lib-y (so it gets removed by the
linker if there are no builtin users).

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Greg Ungerer <gerg@uclinux.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>