[xbus] access type identifier (tag signal)

[stnolting]

New top signal:

xbus_tag_o : out std_ulogic_vector(2 downto 0); -- access tag

• xbus_tag_o(0) P: access is performed from privileged mode (machine-mode) when set
• xbus_tag_o(1) NS: this bit is hardwired to 0 indicating a secure access
• xbus_tag_o(2) I: access is an instruction fetch when set; access is a data access when cleared

Note

This signal is compatible to AXI4's ARPROT and AWPROT signals.