clk: mediatek: mt7622: add missing clock define for MAIN_CORE_EN

Add missing clock for MAIN_CORE_EN. This is a special clock as it's a
gate for the APMIXED clocks required as a parent for CPU clocks.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>

include/dt-bindings/clock/mt7622-clk.h

@@ -169,6 +169,7 @@
 #define CLK_APMIXED_AUD2PLL		6
 #define CLK_APMIXED_TRGPLL		7
 #define CLK_APMIXED_SGMIPLL		8
+#define CLK_APMIXED_MAIN_CORE_EN	9
 
 /* AUDIOSYS */