ASoC: Use SGTL5000_LINREG_VDDD_MASK instead of hardcoded mask value

We have defined SGTL5000_LINREG_VDDD_MASK in sgtl5000.h,
use it instead of hardcoded (0x1 << 4) - 1 for the mask.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Wolfram Sang <w.sang@pengutronix.de>
Acked-by: Liam Girdwood <lrg@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>