include: fpga: adi-axi-common.h: add common regs & defs header

The AXI HDL cores provided for Analog Devices reference designs all share
some common base registers (e.g. version register at address 0x00).

To reduce duplication for this, a common header is added to define these
registers as well as bitfields & macros to work with these registers.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>