lkdtm/stackleak: Fix noinstr violation

Fixes the following warning:

  vmlinux.o: warning: objtool: check_stackleak_irqoff+0x2b6: call to _printk() leaves .noinstr.text section

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/ee5209f53aa0a62aea58be18f2b78b17606779a6.1681320026.git.jpoimboe@kernel.org