x86/cpu/mtrr: Support TOP_MEM2 and get MTRR number

The Hygon Dhyana CPU has a special MSR way to force WB for memory >4GB,
and support TOP_MEM2. Therefore, it is necessary to add Hygon Dhyana
support in amd_special_default_mtrr().

The number of variable MTRRs for Hygon is 2 as AMD's.
Signed-off-by: Pu Wen <puwen@hygon.cn>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: tglx@linutronix.de
Cc: mingo@redhat.com
Cc: hpa@zytor.com
Cc: x86@kernel.org
Cc: thomas.lendacky@amd.com
Link: https://lkml.kernel.org/r/8246f81648d014601de3812ade40e85d9c50d9b3.1537533369.git.puwen@hygon.cn

arch/x86/kernel/cpu/mtrr/cleanup.c

@@ -831,7 +831,8 @@ int __init amd_special_default_mtrr(void)
 {
 	u32 l, h;
 
-	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD)
+	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD &&
+	    boot_cpu_data.x86_vendor != X86_VENDOR_HYGON)
 		return 0;
 	if (boot_cpu_data.x86 < 0xf)
 		return 0;

arch/x86/kernel/cpu/mtrr/mtrr.c

@@ -127,7 +127,7 @@ static void __init set_num_var_ranges(void)
 
 	if (use_intel())
 		rdmsr(MSR_MTRRcap, config, dummy);
-	else if (is_cpu(AMD))
+	else if (is_cpu(AMD) || is_cpu(HYGON))
 		config = 2;
 	else if (is_cpu(CYRIX) || is_cpu(CENTAUR))
 		config = 8;