pinctrl: qcom: ipq8064: Fix naming convention

Drop underscore in spdif_groups to match all other groups.

Signed-off-by: Kumar Gala <galak@codeaurora.org>
Reviewed-by: Andy Gross <agross@codeaurora.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>