objtool: Skip samples subdirectory

The code in the 'samples' subdirectory isn't part of the kernel, so
there's no need to validate it.
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/c4cb4ef635ec606454ab834cb49fc3e9381fb1b1.1579543924.git.jpoimboe@redhat.com

samples/Makefile

 # SPDX-License-Identifier: GPL-2.0
 # Makefile for Linux samples code
+OBJECT_FILES_NON_STANDARD := y
 
 obj-$(CONFIG_SAMPLE_ANDROID_BINDERFS)	+= binderfs/
 obj-$(CONFIG_SAMPLE_CONFIGFS)		+= configfs/