Revert "clk: gxbb: expose CLKID_MMC_PCLK"

This reverts commit e16fb2e635.

Updated documentation from the chip vendor reveals that this clock is
not required for correct operation of the MMC controller. As such, do
not expose it to DT.

Signed-off-by: Michael Turquette <mturquette@baylibre.com>

drivers/clk/meson/gxbb.h

@@ -234,7 +234,7 @@
 #define CLKID_HDMI_PCLK		  63
 #define CLKID_USB1_DDR_BRIDGE	  64
 #define CLKID_USB0_DDR_BRIDGE	  65
-/* CLKID_MMC_PCLK */	       
+#define CLKID_MMC_PCLK		  66
 #define CLKID_DVIN		  67
 #define CLKID_UART2		  68
 #define CLKID_SANA		  69