ASoC: amd: fix uninitialized variable in snd_acp6x_probe()

ASoC: amd: fix uninitialized variable in snd_acp6x_probe()

BugLink: https://bugs.launchpad.net/bugs/1949245
The "index" is potentially used without being initialized on the error
path.

Fixes: fc329c1de498 ("ASoC: amd: add platform devices for acp6x pdm driver and dmic driver")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20211130125633.GA24941@kili
Signed-off-by: Mark Brown <broonie@kernel.org>
(cherry picked from commit d5c137f41352e8dd864522c417b45d8d1aebca68)
Signed-off-by: Hui Wang <hui.wang@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>