arm: socfpga: Drop cyclone5 suffix from board file name

Drop the _cyclone5 suffix from socfpga_cyclone5.c since this file
will contain Arria 5 support as well.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Chin Liang See <clsee@opensource.altera.com>
Acked-by: Dinh Nguyen <dinguyen@opensource.altera.com>
Acked-by: Pavel Machek <pavel@denx.de>
Reviewed-by: Stefan Roese <sr@denx.de>
Cc: Vince Bridgers <vbridger@opensource.altera.com>