Update layerscape u-boot package to LSDK-21.08 and drop patches which
are no longer needed.
The new env variable 'fsl_bootcmd_mcinitcmd_set' is needed to protect
the configured bootcmd and mc_init values. See [1] for more
informations.
[1] b62c174e86
Signed-off-by: Martin Schiller <ms@dev.tdt.de>
