Split the SoCFPGA configuration into SoC-specific part which is
common for all boards (socfpga_cyclone5_common.h) and a board
specific part. There is currently only one board, which is the
generic SoCFPGA board (socfpga_cyclone5.h), but there are more
to come.

This is necessary due to various features of the boards, which
unfortunatelly cannot be autodetected.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Chin Liang See <clsee@altera.com>
Cc: Dinh Nguyen <dinguyen@altera.com>
Cc: Albert Aribaud <albert.u.boot@aribaud.net>
Cc: Tom Rini <trini@ti.com>
Cc: Wolfgang Denk <wd@denx.de>
Cc: Pavel Machek <pavel@denx.de>
Acked-by: Pavel Machek <pavel@denx.de>