drm/vmwgfx: Fix gcc-7.1.1 warning

The current code does not look correct, and the reason for it is
probably lost.  Since this now generates a compiler warning,
fix it to what makes sense.

Cc: <stable@vger.kernel.org>
Reported-by: Arnd Bergmann <arnd@arndb.de>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sinclair Yeh <syeh@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>

drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c

@@ -519,7 +519,7 @@ static int vmw_cmd_invalid(struct vmw_private *dev_priv,
 			   struct vmw_sw_context *sw_context,
 			   SVGA3dCmdHeader *header)
 {
-	return capable(CAP_SYS_ADMIN) ? : -EINVAL;
+	return -EINVAL;
 }
 
 static int vmw_cmd_ok(struct vmw_private *dev_priv,