x86: Add IA32_TSC_AUX MSR and use it

Clean up write_tsc() and write_tscp_aux() by replacing
hardcoded values.

No change in functionality.

Signed-off-by: Sheng Yang <sheng@linux.intel.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
LKML-Reference: <1260942485-19156-4-git-send-email-sheng@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 4ffe09b..ac98d29 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -12,6 +12,7 @@
 #define MSR_FS_BASE		0xc0000100 /* 64bit FS base */
 #define MSR_GS_BASE		0xc0000101 /* 64bit GS base */
 #define MSR_KERNEL_GS_BASE	0xc0000102 /* SwapGS GS shadow */
+#define MSR_TSC_AUX		0xc0000103 /* Auxiliary TSC */
 
 /* EFER bits: */
 #define _EFER_SCE		0  /* SYSCALL/SYSRET */