xtensa: move files under core/include/ into include/

Header files under arch/xtensa/include are considered internal
to architecture. There is really no need for two places to
house architecture internal header files.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>

arch/xtensa/core/CMakeLists.txt

@@ -37,8 +37,6 @@ if("${ZEPHYR_TOOLCHAIN_VARIANT}" STREQUAL "xcc")
   zephyr_library_sources(xcc_stubs.c)
 endif()
 
-zephyr_library_include_directories(include)
-
 add_subdirectory(startup)
 
 # This produces a preprocessed and regenerated (in the sense of gcc

soc/xtensa/dc233c/mmu.c

@@ -12,7 +12,7 @@
 #include <zephyr/arch/xtensa/xtensa_mmu.h>
 #include <zephyr/sys/util.h>
 
-#include "../../arch/xtensa/core/include/xtensa_mmu_priv.h"
+#include <xtensa_mmu_priv.h>
 
 const struct xtensa_mmu_range xtensa_soc_mmu_ranges[] = {
 	{