The 'size' variable is not really needed, and we can also shift constant
in the loop body when masking off existing bits.

Also we do not have to use 64 bit calculations if we take an extra
branch.

[jkosina@suse.cz: fix a small error in changelog]
Suggested-by: NDoug Anderson <dianders@chromium.org>
Signed-off-by: NDmitry Torokhov <dmitry.torokhov@gmail.com>
Reviewed-by: NDouglas Anderson <dianders@chromium.org>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>