Allow note sections to be discarded when they are linked to another discarded secction.

	PR 26681
bfd	* elflink.c (bfd_elf_gc_sections): Do not arbitrarily keep note
	sections which are linked to another section.

ld	* testsuite/ld-elf/pr26681.s: New test.
	* testsuite/ld-elf/pr26681.d: New test driver.
	* testsuite/ld-elf/pr26681.l: New test output.