ipvs: ip_vs_wrr.c: use lib/gcd.c

Remove the private version of the greatest common divider to use
lib/gcd.c, the latter also implementing the a < b case.

[akpm@linux-foundation.org: repair neighboring whitespace because the diff looked odd]
Signed-off-by: Florian Fainelli <florian@openwrt.org>
Cc: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: Takashi Iwai <tiwai@suse.de>
Acked-by: Simon Horman <horms@verge.net.au>
Cc: Julius Volz <juliusv@google.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Patrick McHardy <kaber@trash.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Patrick McHardy <kaber@trash.net>