ASoC: wm8731: initialize the hardware when loading the codec driver

This patch moves the requesting supplies, hardware reset and
initialization from wm8731_probe to wm8731_i2c_probe and wm8731_spi_probe.
So that the codec hardware is initialized when loading the codec driver,
and not when loading the machine driver. This avoids unnecesary hardware
resets and re-initializations when re-loading the machine driver.

Signed-off-by: Sergey Kiselev <sergey.kiselev@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>