ASoC: pxa-ssp: remove .set_pll() and .set_clkdiv() callbacks

The .set_pll() and .set_clkdiv() callbacks are considered legacy and should
not be used anymore. In order to support PXA boards on DT platforms, remove
them and let the code figure out the correct dividers and PLL base
frequencies itself.

Signed-off-by: Daniel Mack <daniel@zonque.org>
Signed-off-by: Mark Brown <broonie@kernel.org>