soc: Separate it8xxx2 related files from the common folder

Some files should be separated from the common folder to
each soc folder for future expansion of the chip.

Signed-off-by: Tim Lin <tim2.lin@ite.corp-partner.google.com>

soc/ite/ec/common/CMakeLists.txt

@@ -1,10 +1,8 @@
 zephyr_include_directories(.)
 
 zephyr_sources(
-  check_regs.c
   soc_irq.S
   soc_common_irq.c
-  vector.S
   )
 
 zephyr_sources_ifdef(CONFIG_PM power.c)

soc/ite/ec/it8xxx2/CMakeLists.txt

@@ -1,4 +1,4 @@
-zephyr_sources(soc.c)
+zephyr_sources(soc.c check_regs.c vector.S)
 zephyr_include_directories(.)
 
 zephyr_library_sources_ifndef(CONFIG_RISCV_ISA_EXT_M __arithmetic.S)