ASoC: Remove special casing for registerless widgets

Since we recently explicitly set the register for registerless widgets
to no register there is no longer any need to special case power updates
for them, we can allow them to be handled with the register compression
code as other widgets are.

As this is the only remaining user of dapm_generic_apply_power() and
dapm_update_bits() also remove those functions.

Noticed-by: Lu Guanqun <guanqun.lu@intel.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>