binutils/testsuite: Tighten the error message check with `strip-13'

binutils/testsuite: Tighten the error message check with `strip-13'

Avoid false positives and actually verify both that an `unsupported
relocation type 0x8f' message is produced and that no other message is,
except for the final `bad value', in the `strip-13' test.  This ensures
that it is a relocation processing error and not a different issue that
has caused `strip' to terminate unsuccessfully, and that the number
representing the unsupported relocation has not been clobbered.

	binutils/
	* testsuite/binutils-all/strip-13.d: Also expect `unsupported
	relocation type 0x8f' error message.