Fix HWPE subsystem for N_HWPE={0,1}

[LuigiGhionda]

This PR fixes the HWPE subsystem of Astral-based pulp cluster in the following non-default scenarios:

• N_HWPE = 1:
• N_HWPE = 0 (HwpePresent=0)

However, it is important to note that the order in which HWPEs are listed in the configuration must reflect the bitmask used in the corresponding HAL function. Otherwise, the HALs will need to be changed. It might be helpful to make the user aware of this requirement somehow.

In addition, it also removes a duplicated call to vopt in the Makefile

[LuigiGhionda]

@ricted98 Since you redesigned the HWPE subsystem for Astral maybe you have some comments/suggestions

[ricted98]

Hi @LuigiGhionda , two questions:

• What was broken in these scenarios?
• Does the static mux not work in the "degenerate" case of a single output?

[LuigiGhionda]

@ricted98

* What was broken in these scenarios?

The problem is with hwpe_sel_int signal definiton which fails when N_HWPE=1 (https://github.com/pulp-platform/pulp_cluster/pull/88/files#diff-6bfef46bbce2076251409cb7cccedbf816d10bcf9dbd66fdb552501a62fd7837L69)

* Does the static mux not work in the "degenerate" case of a single output?

Yes, it can handle the degenerate case, but since its select signal is hwpe_sel_int, I thought to separate the two cases in order only to define it for N_HWPE!=1. However, that part could be modified

[ricted98]

So the problem is the +: operator? If so, we could also think of just adding a parameter to use the mux in all cases.
HWPE_SEL_BITS = N_HWPE == 1 ? 1 : $clog2(N_HWPES). What do you think?