The ffsll function is a lot slower than the __ffs64 built-in which
compiles to a single instruction on 64-bit. It's also nice to avoid
custom versions of standard functions. Note that __ffs == ffs - 1.
Signed-off-by: NIlia Mirkin <imirkin@alum.mit.edu>
Signed-off-by: NBen Skeggs <bskeggs@redhat.com>