ASoC: soc-dapm: Add helper for comparing widget name

Some drivers use one event callback for multiple widgets but still need
to perform a bit different actions based on actual widget.  This is done
by comparing widget name, however drivers tend to miss possible name
prefix.  Add a helper to solve common mistakes.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20231003155710.821315-2-krzysztof.kozlowski@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>