ASoC: pcm186x: Fix device reset-registers trigger value

According to the current device datasheet (TI Lit # SLAS831D, revised
March 2018) the value written to the device's PAGE register to trigger
a complete register reset should be 0xfe, not 0xff. So go ahead and
update to the correct value.

Reported-by: Stephane Le Provost <stephane.leprovost@mediatek.com>
Tested-by: Stephane Le Provost <stephane.leprovost@mediatek.com>
Signed-off-by: Andreas Dannenberg <dannenberg@ti.com>
Acked-by: Andrew F. Davis <afd@ti.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org