configs/cubieboard2: U-Boot needs Python3 & OpenSSL

configs/cubieboard2: U-Boot needs Python3 & OpenSSL

After update of the U-Boot [1] we were missing dependency on Python3,
and so were seeing failures like in [2]:
------------------------->8--------------------
  HOSTLD  scripts/dtc/dtc
scripts/dtc/pylibfdt/libfdt_wrap.c:154:11: fatal error: Python.h: No such file or directory
  154 | # include <Python.h>
      |           ^~~~~~~~~~
compilation terminated.
error: command '/usr/bin/gcc' failed with exit code 1
------------------------->8--------------------

So that get fixed with "BR2_TARGET_UBOOT_NEEDS_PYTHON3=y".
And then once we use Python3, we also need OpenSSL, similarly to [3]
and the likes. So do it with "BR2_TARGET_UBOOT_NEEDS_OPENSSL=y".

Hopefully now all starts to build w/o any issues.

And while at it let's add a bit more structure to the config!

[1] https://git.buildroot.net/buildroot/commit/?id=06f10a88f30b73aaea5c0e0888d7ba9d9a6420f3
[2] https://gitlab.com/buildroot.org/buildroot/-/jobs/1946650570
[3] https://git.buildroot.net/buildroot/commit/?id=cf2a7663ccc6089e98e0d6ec39fa8623749c0c24

Signed-off-by: Alexey Brodkin <[email protected]>
Signed-off-by: Yann E. MORIN <[email protected]>