ld-elf/shared libpr23161c and pr23161c tests

If I understand these tests correctly it is to ensure that _end,
_edata and __bss_start are not made dynamic.  The dynamic reloc tests
are not really necessary.  (We dropped them from pr23161a and pr23161b
tests a while ago without removing the -r from readelf invocation.)
Dropping the reloc tests allows them to run for more targets.

	* testsuite/ld-elf/pr23161c.rd: Rewrite.
	* testsuite/ld-elf/pr23161d.rd: Delete.
	* testsuite/ld-elf/shared.exp (pr23161a, pr23161b): Remove -r
	from readelf check.
	(libpr23161c.so, pr23161c): Likewise, and check expected readelf
	output using the new pr23161c.rd.