The board/altera/socfpga directory is not a generic SoCFPGA machine
anymore, but instead it represents the Altera SoCDK board. To make
matters more complicated, it represents both CycloneV and ArriaV
variant.

On the other hand, nowadays, the content of this board directory is
mostly comprised of QTS-generated header files, while all the generic
code is in arch/arm/mach-socfpga already.

Thus, this patch splits the board/altera/socfpga into a separate
board directory for ArriaV SoCDK and CycloneV SoCDK, so that each
can be populated with the correct QTS-generated header files for
that particular board.

Signed-off-by: Marek Vasut <marex@denx.de>