xhc-hb04: synthesize several per-axis buttons

Users often want to use some buttons on a per-axis basis:

So, if any of the buttons named:
   button-zero, button-goto-zero, button-half
exist, synthesize additional buttons conditioned by the rotary
switch axis selector with names:
   button-zero-x
   button-zero-y
   button-zero-z
   button-zero-a
   button-goto-zero-x
   button-goto-zero-y
   button-goto-zero-z
   button-goto-zero-a
   button-half-x
   button-half-y
   button-half-z
   button-half-a
and create corresponding hal pins:
   xhc-hb04.button-zero-x
   xhc-hb04.button-zero-y
   ...
   etc.