ASoC: wm_adsp: Make DSP name configurable by codec driver

Instead of harcoding that a core must always be called "DSPn"
add a name member to struct wm_adsp so that the owning codec
driver can provide a custom name. This allows for re-use of
the wm_adsp driver with parts where the processing cores are
named differently.

If no name is provided the default DSPn name is used.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Signed-off-by: Mark Brown <broonie@kernel.org>