[rtl] Fix lint "fix" with DbgTriggerEn
[rtl] Fix lint "fix" with DbgTriggerEn

The previous change was wrong: it was trying to define a signal with
DbgHwNumLen bits that contained DbgHwBreakNum - 1. Unfortunately, '1
is *not* the same as a zero-extended version of 1'b1.

lowRISC/ibex,lowRISC/ibex,AmbiML/ibex,AmbiML/ibex,AmbiML/ibex,lowRISC/ibex,AmbiML/ibex,lowRISC/ibex