KVM: selftests: Use port 0x80 in invalid nVMX guest state test

Use port 0x80 instead of 0x2000 to trigger an L2 => L0 VM-Exit in the nVMX
invalid guest state test, so that the test can be expanded to cover RSM in
the L2 => SMI => L2 path without having to manually encode a MOV to DX (the
immediate form of IN only supports an imm8).

Use port 0x80 as it's a well-known port and is used by other tests, e.g. in
the coalesced I/O test.

Link: https://patch.msgid.link/[email protected]
Signed-off-by: Sean Christopherson <[email protected]>

tools/testing/selftests/kvm/x86/vmx_invalid_nested_guest_state.c

@@ -9,7 +9,7 @@
 
 #include "kselftest.h"
 
-#define ARBITRARY_IO_PORT 0x2000
+#define ARBITRARY_IO_PORT 0x80
 
 static struct kvm_vm *vm;
 
@@ -19,8 +19,8 @@ static void l2_guest_code(void)
 	 * Generate an exit to L0 userspace, i.e. main(), via I/O to an
 	 * arbitrary port.
 	 */
-	asm volatile("inb %%dx, %%al"
-		     : : [port] "d" (ARBITRARY_IO_PORT) : "rax");
+	asm volatile("inb $" __stringify(ARBITRARY_IO_PORT) ", %%al"
+		     ::: "rax");
 }
 
 static void l1_guest_code(struct vmx_pages *vmx_pages)