Replace ilog2(__rounddown_pow_of_two(x)) with the equivalent but much
simpler fls(x) - 1.
Reported-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NGuennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: NChris Ball <cjb@laptop.org>