perf build: Ignore intentional differences for the x86 insn decoder

Since we need to build this in !x86, we need to explicitely use the x86
files, not things like asm/insn.h, so we intentionally differ from the
master copy in the kernel sources, add -I diff directives to ignore just
these differences when checking for drift.

Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/n/tip-9qziqjjt120mmz6kyepka9p7@git.kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>