ASoC: sgtl5000: remove useless register write clearing CHRGPUMP_POWERUP

commit c7d910b87d3c8e9fcf4077089ca4327c12eee099 upstream.

The SGTL5000_CHIP_ANA_POWER register is cached. Update the cached
value instead of writing it directly.

Patch inspired by Russell King's more colorful remarks in this
patch:
	https://github.com/SolidRun/linux-imx6-3.14/commit/dd4bf6a



Signed-off-by: Eric Nelson <eric.nelson@boundarydevices.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>