[Bug 256441] U-Boot build for Raspberry Pi 3 (arm64) does not boot from MicroSD card slot when >1 USB storage devices are present

[b***@freebsd.org]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=256441

Bug ID: 256441
Summary: U-Boot build for Raspberry Pi 3 (arm64) does not boot
from MicroSD card slot when >1 USB storage devices are
present
Product: Base System
Version: 13.0-RELEASE
Hardware: Any
OS: Any
Status: New
Severity: Affects Only Me
Priority: ---
Component: arm
Assignee: freebsd-***@FreeBSD.org
Reporter: ***@codelibre.net

Using 13.0-RELEASE image on a 16GB SD card, written using the RPi imager tool.

With 0 or 1 USB storage devices inserted, the system boots fine. With 2-4 USB
storage devices inserted, the system will not boot. Looks like U-Boot is
getting stuck in this situation and not able to read the second stage
bootloader from the SD card mmc0 storage. May be related to #255080

I have transcribed the console output below (may have some minor typos).

With 1 USB storage device inserted:

```
Net: No ethernet found
starting USB...
Bus ***@7e990000: USB DWC2
scanning bus ***@7e980000 for devices... 5 USB Device(s) found
scanning usb for storage devices... 1 Storage Device(s) found
Hit any key to stop autoboot: 0
[boot continues successfully]
```

With 2 USB storage device inserted:

```
Net: No ethernet found
starting USB...
Bus ***@7e990000: USB DWC2
scanning bus ***@7e980000 for devices... 6 USB Device(s) found
scanning usb for storage devices... 2 Storage Device(s) found
Hit any key to stop autoboot: 0
switch to partitions #0, OK
mmc0 is current device
Scanning mmc 0:1...
Found EFI removable media binary efi/boot/bootaa64.efi
libfdt fdt_check_header(): FDT_ERR_BADMAGIC
Scanning disk ***@7e300000.blk...
** Unrecognized filesystem type **
Scanning disk usb_mass_storage.lun0...
** Unrecognized filesystem type **
Scanning disk usb_mass_storage.lun0...
ERROR: Failure to add disk device usb_mass_storage.lun0, r=20
Error: Cannot initialize UEFI sub-system, r=20
125912 bytes read in 125 ms (9.6 MiB/s)
libfdt fdt_check_header(): FDT_ERR_BADMAGIC
Error: Cannot initialize UEFI sub-system, r=20
EFI LOAD FAILED: continuing...
MMC Device 1 not found
no mmc device at slot 1

Device 0: Vendor: Generic Rev: 2.00 Prod: Flash Disk
Type: Removable Hard Disk
Capacity: 7680.0 MB = 7.5 GB (15728640 x 512)
... is now current device
** Unrecognized filesystem type **
Waiting for Ethernet connection... done.
BOOTP broadcast 1
...
[boot never succeeds]
```