Staging: hv: use the correct #ifdef for x86-64

x86-64 needs a different config check.  Thanks to Hank for the debugging
to determine the fix for this.

Cc: Hank Janssen <hjanssen@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/staging/hv/Hv.c

@@ -165,7 +165,7 @@ HvDoHypercall (
     void*   Output
     )
 {
-#ifdef x86_64
+#ifdef CONFIG_X86_64
     UINT64 hvStatus=0;
     UINT64 inputAddress = (Input)? GetPhysicalAddress(Input) : 0;
 	UINT64 outputAddress = (Output)? GetPhysicalAddress(Output) : 0;