lib/flex_proportions.c: cleanup __fprop_inc_percpu_max

lib/flex_proportions.c: cleanup __fprop_inc_percpu_max

If the given type has fraction smaller than max_frac/FPROP_FRAC_BASE, the
code could be modified to call __fprop_inc_percpu() directly and easier to
understand.  After this patch, fprop_reflect_period_percpu() will be
called twice, and quicky return on pl->period == p->period test, so it
would not result to significant downside of performance.

Thanks for Jan's guidance.

Signed-off-by: Tan Hu <tan.hu@zte.com.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: <xue.zhihong@zte.com.cn>
Cc: Yi Wang <wang.yi59@zte.com.cn>
Cc: <wang.liang82@zte.com.cn>
Link: http://lkml.kernel.org/r/1589004753-27554-1-git-send-email-tan.hu@zte.com.cn
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>