Since 0001-CMD-read-string-from-fileinto-env.patch is in the global
directory to be applied for U-Boot, drop it from the Raspberry Pi
specific patch directory.
* Re-add patches missed with U-Boot 2021.04-rc4 upgrade
Also add patches for Raspberry Pi again.
* Regenerate patches for U-Boot 2021.04
* Update to U-Boot 2021.04
Bump to the latest U-Boot release 2021.04-rc4. This alows to drop quite
some patches which have been sent to the mailing list or picked from the
mailing list and have been merged upstream now.
The patch causes U-Boot freezes in some configurations. The root cause
is that U-Boot does not allow to use the bss section in pre-relocation
code (which is where the UART is used). Drop the patch as it is not
required currently.
See also:
http://u-boot.10912.n7.nabble.com/RPi4-U-Boot-freeze-td424432.html#a427198
