tools arch x86: Sync the msr-index.h copy with the kernel sources

To pick up the changes from these csets:

  159013a7ca ("x86/its: Enumerate Indirect Target Selection (ITS) bug")

That cause no changes to tooling as it doesn't include a new MSR to be
captured by the tools/perf/trace/beauty/tracepoints/x86_msr.sh script,
for instance:

  $ tools/perf/trace/beauty/tracepoints/x86_msr.sh | head
  static const char * const x86_MSRs[] = {
  	[0x00000000] = "IA32_P5_MC_ADDR",
  	[0x00000001] = "IA32_P5_MC_TYPE",
  	[0x00000010] = "IA32_TSC",
  	[0x00000017] = "IA32_PLATFORM_ID",
  	[0x0000001b] = "IA32_APICBASE",
  	[0x00000020] = "KNC_PERFCTR0",
  	[0x00000021] = "KNC_PERFCTR1",
  	[0x00000028] = "KNC_EVNTSEL0",
  	[0x00000029] = "KNC_EVNTSEL1",
  $

Just silences this perf build warning:

  Warning: Kernel ABI header differences:
    diff -u tools/arch/x86/include/asm/msr-index.h arch/x86/include/asm/msr-index.h

Please see tools/include/uapi/README for further details.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Link: https://lore.kernel.org/r/20250519214126.1652491-3-acme@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/arch/x86/include/asm/msr-index.h

@@ -211,6 +211,14 @@
 						 * VERW clears CPU Register
 						 * File.
 						 */
+#define ARCH_CAP_ITS_NO			BIT_ULL(62) /*
+						     * Not susceptible to
+						     * Indirect Target Selection.
+						     * This bit is not set by
+						     * HW, but is synthesized by
+						     * VMMs for guests to know
+						     * their affected status.
+						     */
 
 #define MSR_IA32_FLUSH_CMD		0x0000010b
 #define L1D_FLUSH			BIT(0)	/*