ipa: Fix up ipa modref option help texts

ipa: Fix up ipa modref option help texts

This fixes
FAIL: compiler driver --help=common option(s): "^ +-.*[^:.]$" absent from output: "  --param=modref-max-tests=   Maximum number of tests perofmed by modref query"
FAIL: compiler driver --help=optimizers option(s): "^ +-.*[^:.]$" absent from output: "  -fipa-modref                Perform interprocedural modref analysis"

2020-09-22  Jakub Jelinek  <jakub@redhat.com>

	* common.opt (-fipa-modref): Add dot at the end of option help.
	* params.opt (--param=modref-max-tests=): Likewise.