xhc-hb04.tcl: support fractional scale factors

fractional scale values will not work directly
since axis.N.jog-counts is integer (s32) and
suffers truncation.

Support fractional scales by apply prescaling with:
     axis.N.jog-counts * kvalue  (via pendant_util.scale$idx)
and
     axis.N.jog-scale  / kvalue

(kvalue is hardcoded to 1000000)

Signed-off-by: Dewey Garrett <dgarrett@panix.com>