OpenSystemsDevelopment / usbboot

The MSD (and secure-boot variant) bootloader has been updated to
fully initialise SDRAM in order to resolve problems when using
this method to run Linux ramdisks / initrd.
Therefore, MSD boot will not work on a system with a blank or
corrupted EEPROM. If so, an error message will be output to the
UART and the EEPROM should be programmed using the recovery
option.

Update this binary to the latest.
Also rebuilt the windows installer

Update bootcode4.bin to avoid some blocking operations which can cause
USB errors.

* Add 2711 bootcode and FW binaries with the 4 suffix.
* Use the device descriptor to select the correct bootcode and
  hack it so that bootcode.bin translates to bootcode4.bin on a
  Pi4 allowing the files to remain in the same directory.
* Add the latest best for recovery.bin and pieeprom.bin for CM4
* Update the installer.

Move the second stage preparation until after the device descriptor
has been retrieved because BCM2711 needs a different bootcode.bin.

If the '-d' argument specified then check for bootcode.bin in the
specified directory and don't fail over to the embedded fmem files.

Remove the default 'msd' directory and the references to /usr/share
because the behaviour conflicts with the original change to use
the fmem files.