MMU should not be present when using config cv32a6_imac_sv0

[Gchauvon]

In ariane_pkg.sv parameter MMU_PRESENT is always set. It should not be the case since cv32a6_imac_sv0 configuration does not have MMU.

https://github.com/openhwgroup/cva6/blob/e4b48a794b0229eeb9264a6b3f459c86545d1d85/core/include/ariane_pkg.sv#L625

I recommend to make this parameter depends on which cva6 config package we use.

• cv32a6_imac_sv0_config_pkg.sv
• cv32a6_imac_sv32_config_pkg.sv
• cv32a6_imafc_sv32_config_pkg.sv
• cv64a6_imafc_sv39_config_pkg.sv

I believe we should also modify parameter like SV_MODE, SV, VLEN ? accordingly. https://github.com/openhwgroup/cva6/blob/e4b48a794b0229eeb9264a6b3f459c86545d1d85/core/include/riscv_pkg.sv#L48-L49

Some more RTL may or may not need changes if MMU is disabled but I didn't look into that very deeply.