clk: mediatek: mt7986: rename CB_CKSQ_40M to TOP_XTAL

Upstream kernel linux clock include use TOP_XTAL instead of CB_CKSQ_40M.
Rename this clock to the upstream kernel in preparation for support of
OF_UPSTREAM.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
diff --git a/arch/arm/dts/mt7986.dtsi b/arch/arm/dts/mt7986.dtsi
index 30b5a89..276f82f 100644
--- a/arch/arm/dts/mt7986.dtsi
+++ b/arch/arm/dts/mt7986.dtsi
@@ -178,7 +178,7 @@
 		clocks = <&infracfg_ao CK_INFRA_UART0_CK>;
 		assigned-clocks = <&topckgen CK_TOP_UART_SEL>,
 				  <&infracfg_ao CK_INFRA_UART0_SEL>;
-		assigned-clock-parents = <&topckgen CK_TOP_CB_CKSQ_40M>,
+		assigned-clock-parents = <&topckgen CK_TOP_XTAL>,
 					 <&infracfg CK_INFRA_UART>;
 		mediatek,force-highspeed;
 		status = "disabled";