tools: mkimage: Update U-Boot to version 2021.01

tools: mkimage: Update U-Boot to version 2021.01

* The fit image is now created with 0666 permission in upstream U-Boot
  remove our patch switch creates it with 0744
* The generated/autoconf.h file is created now as an empty file, it is
  not needed to remove this include any more.
* Upstream lib/rsa/rsa-sign.c now includes stdlib.h instead of malloc.h
* ALIGN_MASK was moved to imagetool.h, own patch should not be needed
  any more.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>