pinctrl: meson: fix unused variable warning

The kernel test robot reported a warning as below:
>> drivers/pinctrl/meson/pinctrl-meson-s4.c:178:27: warning: unused variable 'tdm_sclk1_c_pins' [-Wunused-const-variable]
   static const unsigned int tdm_sclk1_c_pins[]            = { GPIOC_3 };

Fix it by adding missing description about this pins

Fixes: 775214d3 ("pinctrl: meson: add pinctrl driver support for Meson-S4 Soc")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Qianggui Song <qianggui.song@amlogic.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://lore.kernel.org/r/20220330023720.18238-1-qianggui.song@amlogic.comSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/meson/pinctrl-meson-s4.c

@@ -575,6 +575,7 @@ static struct meson_pmx_group meson_s4_periphs_groups[] = {
 	GROUP(tdm_d2_c,			4),
 	GROUP(tdm_d3_c,			4),
 	GROUP(tdm_fs1_c,		4),
+	GROUP(tdm_sclk1_c,		4),
 	GROUP(mclk_1_c,			4),
 	GROUP(tdm_d4_c,			4),
 	GROUP(tdm_d5_c,			4),
@@ -936,7 +937,7 @@ static const char * const iso7816_groups[] = {
 };
 
 static const char * const tdm_groups[] = {
-	"tdm_d2_c", "tdm_d3_c", "tdm_fs1_c", "tdm_d4_c", "tdm_d5_c",
+	"tdm_d2_c", "tdm_d3_c", "tdm_fs1_c", "tdm_d4_c", "tdm_d5_c", "tdm_sclk1_c",
 	"tdm_fs1_d", "tdm_d4_d", "tdm_d3_d", "tdm_d2_d", "tdm_sclk1_d",
 	"tdm_sclk1_h", "tdm_fs1_h", "tdm_d2_h", "tdm_d3_h", "tdm_d4_h",
 	"tdm_d1", "tdm_d0", "tdm_fs0", "tdm_sclk0", "tdm_fs2", "tdm_sclk2",