Add ia64*-*-* to the list of obsolete targets

The following deprecates ia64*-*-* for GCC 14.  Since we plan to
force LRA for GCC 15 and the target only has slim chances of getting
updated this notifies people in advance.  Given both Linux and
glibc have axed the target further development is also made difficult.
There is no listed maintainer for ia64 either.

	PR target/90785
gcc/
	* config.gcc: Add ia64*-*-* to the list of obsoleted targets.

contrib/
	* config-list.mk (LIST): --enable-obsolete for ia64*-*-*.