Documentation/kcov: Include types.h in the example.

The first example code has includes at the top, the following two
example share that part. The last example (remote coverage collection)
requires the linux/types.h header file due its __aligned_u64 usage.

Add the linux/types.h to the top most example and a comment that the
header files from above are required as it is done in the second
example.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20210830172627.267989-2-bigeasy@linutronix.de

Documentation/dev-tools/kcov.rst

@@ -50,6 +50,7 @@ program using kcov:
     #include <sys/mman.h>
     #include <unistd.h>
     #include <fcntl.h>
+    #include <linux/types.h>
 
     #define KCOV_INIT_TRACE			_IOR('c', 1, unsigned long)
     #define KCOV_ENABLE			_IO('c', 100)
@@ -251,6 +252,8 @@ selectively from different subsystems.
 
 .. code-block:: c
 
+    /* Same includes and defines as above. */
+
     struct kcov_remote_arg {
 	__u32		trace_mode;
 	__u32		area_size;