style: Apply clang-format to C/C++ source files

Applied consistent code formatting using clang-format to all C/C++ source
and header files in the 'software/' directory.

software/apps/gateway/src/main.c

@@ -6,7 +6,8 @@
 
 #include <zephyr/kernel.h>
 
-int main(void) {
-  printk("Hello from Gateway!\n");
-  return 0;
+int main(void)
+{
+	printk("Hello from Gateway!\n");
+	return 0;
 }