configure: Update --help output for --with-multilib-list

The list of architectures that support the option is incomplete.

Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
Reviewed-by: Jim Wilson <jimw@sifive.com>

gcc/ChangeLog:

	* configure.ac: Fix --with-multilib-list description.
	* configure: Regenerate.
2 files changed