[circt] Remove -verify-each=false firtool option (#2949)

Remove the default option of "-verify-each=false" to firtool.  This
shouldn't be necessary and shouldn't be turned on.  I had left this on
when doing some performance comparisons and it made its way into
upstream chisel.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@sifive.com>