added efm32gg12 family cmsis

Signed-off-by: Rafael Silva <silvagracarafael@gmail.com>

.gitmodules

@@ -113,3 +113,6 @@
 [submodule "lib/CMSIS_5"]
 	path = lib/CMSIS_5
 	url = https://github.com/ARM-software/CMSIS_5.git
+[submodule "hw/mcu/silabs/cmsis-dfp-efm32gg12b"]
+	path = hw/mcu/silabs/cmsis-dfp-efm32gg12b
+	url = https://github.com/cmsis-packs/cmsis-dfp-efm32gg12b

hw/mcu/silabs/cmsis-dfp-efm32gg12b

@@ -0,0 +1 @@
+Subproject commit f1c31b7887669cb230b3ea63f9b56769078960bc