x86, perf: Fix the dependency of the x86 insn decoder selftest

Since x86 instruction decoder is not only for kprobes,
it should be tested when the insn.c is compiled.
(e.g. perf is enabled but kprobes is disabled)

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: cbe5c34c ("x86: Compile insn.c and inat.c only for KPROBES")
Signed-off-by: Ingo Molnar <mingo@kernel.org>