ASoC: cs42l52: fix master playback mute mask.

The mask should define the bits to change in the register, not the
bits to preserve.

This fixes the inadvertent changes of the "Headphone Analog Gain"
value during mute/unmute.

Signed-off-by: Nicolas Schichan <nschichan@freebox.fr>
Acked-by: Brian Austin <brian.austin@cirrus.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>