x86: fix bootup crash in native_read_tsc()

fix bootup crash in native_read_tsc() that was reported on an Athlon-XP
and bisected. The correct feature boundary for X86_FEATURE_MFENCE_RDTSC
is not XMM but XMM2.

Signed-off-by: Ingo Molnar <[e-mail]>
Acked-by: H. Peter Anvin <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/x86/kernel/cpu/amd.c

···
 	if (c->x86 < 6)
 		clear_bit(X86_FEATURE_MCE, c->x86_capability);
 
-	if (cpu_has_xmm)
+	if (cpu_has_xmm2)
 		set_bit(X86_FEATURE_MFENCE_RDTSC, c->x86_capability);
 }