Replace uvma_axi_macros with non-random values in the cfg object

[Mike Thompson]

As of afb560d, there is a set of SystemVerilog macros in uvma_axi_macros that define a set of limits for various random members of uvma_axi5 agent. The use of SV macros for configuration should be avoided as they are global in scope and subect to change at compile-time.

These macros should be replace with non-random members of the cfg class.