[RCAR] Fix gcc 10 build failed on u-boot and kernel.

[RCAR] Fix gcc 10 build failed on u-boot and kernel.

* cherry pick upstream patch to fix u-boot and linux kernel on gcc
  10 build issue.

Bug-AGL: [SPEC-3617]

Signed-off-by: Ronan Le Martret <ronan.lemartret@iot.bzh>
Change-Id: I0c85938287861a8efc328b5c08bbf364027f6473
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl/+/25416
Tested-by: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
ci-image-build: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
ci-image-boot-test: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>
Reviewed-by: Stéphane Desneux <stephane.desneux@iot.bzh>