gas: xtensa: fix comparison of trampoline chain symbols

gas: xtensa: fix comparison of trampoline chain symbols

Don't use address where symbol gets resolved, as during section
relaxation symbols will slide, instead canonicalize symbols and check
that they are are the same.
This fixes a bug when a relaxed jump goes into the wrong trampoline.

gas/
2017-12-07  Max Filippov  <jcmvbkbc@gmail.com>

	* config/tc-xtensa.c (xg_order_trampoline_chain): Replace
	xg_order_trampoline_chain_entry call with check for
	canonicalized symbol equality and offset equality.