Revise "ld testsuite use of notarget"

Revise "ld testsuite use of notarget"

git commit 624940689a wrongly changed fill.d and fill16.d notarget
entries to xfail, so revert that change and instead replace notarget
with skip.  The two tests are complementary.

This patch also modifies the pr20022 test to use .data, avoiding
xfails on targets that complain about dynamic relocations in .text.
This shows a bug in metag which discards section _foo in pr2022.so.

	* testsuite/ld-elf/hash.d: Comment on mips xfail.
	* testsuite/ld-gc/pr20022b.s: Use .data not .text.
	* testsuite/ld-gc/pr20022.d: Remove xfails.
	* testsuite/ld-scripts/fill.d: Revert most of last patch, but use
	skip rather than notarget.
	* testsuite/ld-scripts/fill16.d: Likewise.