unicore32: fix build error for find bitops

Remove the __uc32_ prefix in find bitops functions.
Move find_* macros behind asm-generic/bitops.h inclusion.
see commit <19de85ef>
  bitops: add #ifndef for each of find bitops
also see commit <63e424c8>
  arch: remove CONFIG_GENERIC_FIND_{NEXT_BIT,BIT_LE,LAST_BIT}

Signed-off-by: Guan Xuetao <gxt@mprc.pku.edu.cn>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Acked-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>