dts: stm32f412Xg: Factorize package definitions

2 identical packages were defined for stm32f412 SoC, invariant "g".
Merge them in new sinclge stm32f412Xg.dtsi.
Update matching boards accordinlgy.

Signed-off-by: Erwan Gouriou <[email protected]>

Author: erwango

boards/arm/96b_argonkey/96b_argonkey.dts

@@ -5,7 +5,7 @@
  */
 
 /dts-v1/;
-#include <st/f4/stm32f412cg.dtsi>
+#include <st/f4/stm32f412Xg.dtsi>
 
 / {
 	model = "Tocoding Argonkey 96boards";

boards/arm/nucleo_f412zg/nucleo_f412zg.dts

@@ -5,7 +5,7 @@
  */
 
 /dts-v1/;
-#include <st/f4/stm32f412zg.dtsi>
+#include <st/f4/stm32f412Xg.dtsi>
 
 / {
 	model = "STMicroelectronics STM32F412ZG-NUCLEO board";

boards/arm/stm32f412g_disco/stm32f412g_disco.dts

@@ -5,7 +5,7 @@
  */
 
 /dts-v1/;
-#include <st/f4/stm32f412zg.dtsi>
+#include <st/f4/stm32f412Xg.dtsi>
 
 / {
 	model = "STMicroelectronics STM32F412G-DISCO board";