license: cleanup: add SPDX Apache-2.0 license identifier

Update the files which contain no license information with the
'Apache-2.0' SPDX license identifier.  Many source files in the tree are
missing licensing information, which makes it harder for compliance
tools to determine the correct license.

By default all files without license information are under the default
license of Zephyr, which is Apache version 2.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>

soc/xtensa/esp32/CMakeLists.txt

@@ -1,3 +1,5 @@
+# SPDX-License-Identifier: Apache-2.0
+
 zephyr_sources(
   soc.c
   esp32-mp.c

soc/xtensa/intel_s1000/CMakeLists.txt

@@ -1,3 +1,5 @@
+# SPDX-License-Identifier: Apache-2.0
+
 zephyr_library()
 zephyr_library_include_directories(${ZEPHYR_BASE}/drivers)
 zephyr_library_sources(soc.c)

soc/xtensa/intel_s1000/dts_fixup.h

@@ -1,3 +1,5 @@
+/* SPDX-License-Identifier: Apache-2.0 */
+
 /* SoC level DTS fixup file */
 
 #define DT_UART_NS16550_PORT_0_BASE_ADDR	DT_NS16550_80800_BASE_ADDRESS

soc/xtensa/sample_controller/CMakeLists.txt

@@ -1 +1,3 @@
+# SPDX-License-Identifier: Apache-2.0
+
 # intentionally left empty