ASoC: dapm: Only clear paths we've walked

When clearing the walked flags there is no need to clear all paths, we
only need to clear the paths we actually walked. This means we can split
dapm_clear_walk() into input and output versions and rather than going
through all DAPM paths we can recurse down the path until we encounter
paths we have not yet walked.

This reduces the number of operations we need to perform and improves
cache locality.

[Pulled out of the vendor tree that the patch was originally generated
for by me, any bugs were introduced in that process -- broonie]

Signed-off-by: Ryo Tsutsui <Ryo.Tsutsui@wolfsonmicro.com>
Acked-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>