loader.efi: |= the boot flags how

[imp]

Summary

how is assumed to be 0, so we directly assign to it. It might not always
be 0, so or-in these bits.

Sponsored by: Netflix

stand/efi/loader/main.c

if (rv != EFI_SUCCESS) {
                  * make video primary, otherwise just make serial primary. In
                  * either case, try to use both the 'efi' console which will use
                  * the GOP, if present and serial. If there's an EFI BIOS that
                  * omits this, but has a serial port redirect, we'll
                  * unavioidably get doubled characters (but we'll be right in
                  * all the other more common cases).
                  */
                 if (efi_has_gop())
-                        how = RB_MULTIPLE;
+                        how |= RB_MULTIPLE;
                 else
-                        how = RB_MULTIPLE | RB_SERIAL;
+                        how |= RB_MULTIPLE | RB_SERIAL;
                 setenv("console", "efi,comconsole", 1);
                 goto out;
         }
         ep = buf + sz;
         node = (EFI_DEVICE_PATH *)buf;
         while ((char *)node < ep) {
                 if (IsDevicePathEndType(node)) {
                         if (pci_pending && vid_seen == 0)