HID: hid-example: fix some build issues

samples/hid-example.o needs some Kconfig and Makefile additions in order
to build.  It should use <linux/*.h> headers from the build tree, so use
HEADERS_CHECK to require that those header files be present.

Change the kconfig symbol from tristate to bool since userspace cannot be
built as loadable modules.

However, I don't understand why the userspace header files are not present
as reported in Andrew's build log, since it builds OK on x86_64 without
any of these changes.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Alan Ott <alan@signal11.us>
Cc: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>