ASoC: codec: wm8960: Stop when a matching PLL freq is found

When a matching PLL freq is found, searching continues even this is
not necessary. The problem was introduced with the following refactoring
commit 84fdc00d ("ASoC: codec: wm9860: Refactor PLL out freq search)

Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
Signed-off-by: Mark Brown <broonie@kernel.org>