ASoC: dapm: Break out of widget search when source and sink are located

Currently snd_soc_dapm_add_route will continue to search the widget list
even after both the source and sink for the route have been located.
This patch breaks out of the search when both are located giving a
small improvement in probe time for drivers.

Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@kernel.org>