floogen: Render endpoint enums to index into Sam

[fischeti]

Adds an initial enum sam_idx_e in the generated package which can be used to index into the System Address Map (SAM). The index is not equal to the ep_ide_e, since there are potentially multiple address ranges for each endpoint.

If an endpoint has multiple address ranges, the user can also give a description of each of them (which is optional). For instance:

  - name: "hostcore"
    addr_range:
      - start: 0x4000
        end: 0x5000
        desc: "uart"
      - start: 0x7000
        end: 0x8000
        desc: "spi"

which will result in:

  typedef enum logic [2:0] {
    ...
    HostcoreUartSamIdx = 4,
    HostCoreSpiSamIdx = 5,
    ...
  } sam_idx_e;