ound/core/pcm_timer.c: use lib/gcd.c

Make sound/core/pcm_timer.c use lib/gcd.c

Signed-off-by: Florian Fainelli <florian@openwrt.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
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