target/microblaze: Add use-non-secure property

target/microblaze: Add use-non-secure property

This property is used to control the security of the following interfaces
on MicroBlaze:
M_AXI_DP - data interface
M_AXI_IP - instruction interface
M_AXI_DC - dcache interface
M_AXI_IC - icache interface

It works by enabling or disabling the use of the non_secure[3:0] signals.

Interfaces and their corresponding values are taken from:
https://www.xilinx.com/support/documentation/sw_manuals/xilinx2020_2/ug984-vivado-microblaze-ref.pdf
page 153.

Signed-off-by: Joe Komlodi <komlodi@xilinx.com>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Tested-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Message-Id: <1611274735-303873-2-git-send-email-komlodi@xilinx.com>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>