OpenSystemsDevelopment / usbboot

Merge https://github.com/timg236/cm4-scripts/pull/1 to remove the
LED activity flashing because this conflicts with EMMC_EN_N_1V8
on CM3.

I've reverted the change that removed the explict modprobe of
libcomposite becuase that broke the gadgetfs support for me on CM4.

Add option to look for CM with specific USB path.

Force device/peripheral mode instead of relying on the OTG pin
because this might not work on CM4S.

Replace duplicated bootcode4.bin with links to bootcode4.bin / recovery.bin

This also resolve a startup issue CM4-S

Sync this with the version in tools. TODO - change the scripts
to use the version in tools instead.

bootcode4: Improved DDR setup for old (or missing) EEPROM images

Ideally, the bootloader EEPROM should be updated before using
bootcode4 to run Linux so that full SDRAM init can be loaded.
This version fails over to a generic slow configuration if BRCM
DDR FW is not found.

Not all Linux systems have pkg-config installed by default, so include
it in the list of things to install.

Update Readme.md

Add missing products which do USB device boot.

Copy edit

Ensure consistency within repo and with style guide.

documentation: Secure boot quick start / walkthough

The secure-boot-example/boot.img has been replaced with the
mass-storage-gadget Linux OS image because it already supported
login, hdmi and ethernet.

Typo fixes from @dp111 (who obviously has too much time on his hands).

Revert binary to usbboot 4608d57c4d57dde19cc14988ee14702868d394bd

msd: Fix support for older EEPROM release in on 2711

Update EEPROM, recovery.bin and bootcode4.bin to 2022-04-26

Previously two commits added a fallback fmemopen for OS X/BSD that
didn't support fmemopen, then fixed some of the ifdef logic around it.
Unforunately the logic was backwards, as libc implementations do not
define _POSIX_C_SOURCE in order to advertise features.  Instead the
user defines _POSIX_C_SOURCE to control which definitions are
available.

Check _POSIX_VERSION to see if the libc is new enough to implement
fmemopen.  If it is too old, assume that we're on a BSD compatible
system and use the fallback fmemopen that depends on funopen.
This solves the problem for some environments, but is still incorrect
as it will try to use the fallback even on a system that does not
include funopen.

Fixes: 45c7237 (Fixup for recent firmware inclusion changes (#34))
Fixes: 17f6b01 (Fix cross-platform building)

Add inline comments about boot order

Add no sudo hint