tools: sync find_bit() implementation

Sync find_first_bit() and find_next_bit() implementation with the
mother kernel.

Also, drop unused find_last_bit() and find_next_clump8().

Signed-off-by: Yury Norov <yury.norov@gmail.com>

tools: sync tools/bitmap with mother linux

Remove tools/include/asm-generic/bitops/find.h and copy
include/linux/bitmap.h to tools. find_*_le() functions are not copied
because not needed in tools.

Signed-off-by: Yury Norov <yury.norov@gmail.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>