binutils: fix xtensa trampolines search code for conditional branches

This fixes the following build errors seen when assembling huge files
produced by gcc:
  Error: jump target out of range; no usable trampoline found
  Error: operand 1 of 'j' has out of range value '307307'

Fixes:
  http://autobuild.buildroot.net/results/545/545168d9caf3bdb3dd3eb3bae58ba9db8a33384a/



Backported from: d92b6eece424f0ad35d96fdd85bf207295e8c4c3
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>