x86/cpu: Drop unused X86_VENDOR_* values

Xen only has CPU drivers for Intel, Centaur and AMD.  All other contributions
to X86_VENDOR_NUM simply make the cpu_devs[] array longer, reducing the
efficiency of get_cpu_vendor()

There is one remaning hidden reference to X86_VENDOR_CYRIX in the MTRR code.
However, as far as I can tell, Cyrix never realeased a 64bit processor.  It is
therefore dead code.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

xen/arch/x86/cpu/mtrr/main.c

@@ -94,7 +94,7 @@ static void __init set_num_var_ranges(void)
 		rdmsrl(MSR_MTRRcap, config);
 	} else if (is_cpu(AMD))
 		config = 2;
-	else if (is_cpu(CYRIX) || is_cpu(CENTAUR))
+	else if (is_cpu(CENTAUR))
 		config = 8;
 	num_var_ranges = config & 0xff;
 }

xen/include/asm-x86/processor.h

@@ -20,15 +20,9 @@
  * CPU vendor IDs
  */
 #define X86_VENDOR_INTEL 0
-#define X86_VENDOR_CYRIX 1
-#define X86_VENDOR_AMD 2
-#define X86_VENDOR_UMC 3
-#define X86_VENDOR_NEXGEN 4
-#define X86_VENDOR_CENTAUR 5
-#define X86_VENDOR_RISE 6
-#define X86_VENDOR_TRANSMETA 7
-#define X86_VENDOR_NSC 8
-#define X86_VENDOR_NUM 9
+#define X86_VENDOR_AMD 1
+#define X86_VENDOR_CENTAUR 2
+#define X86_VENDOR_NUM 3
 #define X86_VENDOR_UNKNOWN 0xff
 
 /*