nios2: add Max10 defconfig

Max10 is a FPGA device. This patch adds defconfig based on Max10 hardware
reference design. Design is intended to run on Max10 development kit.

Signed-off-by: Chee Nouk Phoon <cnphoon@altera.com>
Signed-off-by: Ley Foon Tan <lftan@altera.com>