socfpga: Move board/socfpga_cyclone5 to board/socfpga

socfpga: Move board/socfpga_cyclone5 to board/socfpga

Because the SOCFPGA platform will include support for Cyclone V and
Arria V FPGA parts, renaming socfpga_cyclone5 folder to socfpga to
be more generic.

Signed-off-by: Dinh Nguyen <dinguyen@altera.com>
Reviewed-by: Pavel Machek <pavel@denx.de>
Cc: Chin Liang See <clsee@altera.com>
Cc: Wolfgang Denk <wd@denx.de>
CC: Pavel Machek <pavel@denx.de>
Cc: Tom Rini <trini@ti.com>
v2:
- Add Reviewed-by: Pavel Machek
- Cc: Tom Rini