ARM: dts: socfpga: fpga manager data is 32 bits

Adjust regs property for the FPGA manager data register to
properly reflect that it is a single 32 bit register.

Signed-off-by: Dalon Westergreen <dwesterg@altera.com>
Signed-off-by: Alan Tull <atull@opensource.altera.com>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>