ASoC: Set correct name for WM8753 rec mixer output

Rob Sims wrote:

"I can't seem to turn on register 0x17, bit 3 in the sound chip, except
by codec_reg_write; the mixer lacks direct or indirect control.  It
seems there are two names for the output of the rec mixer:
Capture ST Mixer
Playback Mixer

Would the following do the trick?"

I confirm that this solves the audio problems I was having.

Signed-off-by: Jonas Bonn <jonas.bonn@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>