ASoC: sgtl5000: Fix suspend/resume

Commit 8419caa7

 ("ASoC: sgtl5000: Do not disable regulators in
SND_SOC_BIAS_OFF") causes the sgtl5000 to fail after a suspend/resume
sequence:

Playing WAVE '/media/a2002011001-e02.wav' : Signed 16 bit Little
Endian, Rate 44100 Hz, Stereo
aplay: pcm_write:2051: write error: Input/output error

The problem is caused by the fact that the aforementioned commit
dropped the cache handling, so re-introduce the register map
resync to fix the problem.

Suggested-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: <stable@vger.kernel.org>