* Linux: Update kernel 5.15.25
Use highest available kernel version in Buildroot 2021.08 (5.13)
* Update Hardkernel patches to Linux 5.15
* Update generic-x86-64/ova kernel config/patches for 5.15
* Drop Intel e1000e Sourceforge driver
The driver has been discontinued sometime last year. The main reason the
out-of-tree kernel has been enabled was for support for the i219-V
network chips which meanwhile are supported in mainline.
* Rename Intel NUC machine to Generic x86-64
The Intel NUC machine has evolved and supports various x86-64 machines
today. Rename the board.
Note that this does not address the migration issue. This will be
handled separately.
* Update Scripts/Documentation
