m68k: bitops - offset == ((long)p - (long)vaddr) * 8

Hence use "offset" in find_next_{,zero_}bit(), like is already done for
find_next_{,zero_}bit_le()

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Andreas Schwab <schwab@linux-m68k.org>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>