RISC-V: Don't report warnings when linking different privileged spec objects.

RISC-V: Don't report warnings when linking different privileged spec objects.

Since only the abandoned privileged spec v1.9.1 will have conflict csrs, to
keep the compatible we still report warnings when linking privileged spec
v1.9.1 objects with others.  But don't report warnings for other compatible
cases because it is actually a bit noisy and useless...

bfd/
	* elfnn-riscv.c (riscv_merge_attributes): Only report warnings when
	linking the abandoned privileged spec v1.9.1 object with others.
ld/
	* testsuite/ld-riscv-elf/attr-merge-priv-spec-failed-01.d: Removed.
	* testsuite/ld-riscv-elf/attr-merge-priv-spec-failed-02.d: Removed.
	* testsuite/ld-riscv-elf/attr-merge-priv-spec-failed-03.d: Removed.
	* testsuite/ld-riscv-elf/attr-merge-priv-spec-failed-04.d: Removed.
	* testsuite/ld-riscv-elf/attr-merge-priv-spec-failed-05.d: Removed.
	* testsuite/ld-riscv-elf/attr-merge-priv-spec-failed-06.d: Removed.
	* testsuite/ld-riscv-elf/ld-riscv-elf.exp: Updated.