More compact register attribute definitions

[markuslsra]

Add the possibility to write field attributes in a more compact way.

E.g sth like:

        width 36
        software {
            ro
        }
        hardware {
            wo
            no_wen
        }

combines to

          attributes { width 36  sw_ro  hw_wo  hw_no_wen }

This could compact the size of the RF definitions... ( E.g. at the moment 35 hardware register easily need 1500 lines of code as description)

[TM90]

For a simpler and a more consistent implementation

field test{
    width 32
    software ro
    hardware {
         wo
         no_wen
    }
}

would combine to:

field test {width 32; sw_ro; hw_wo; hw_no_wen}