Fix trampolines search code for conditional branches

Fix trampolines search code for conditional branches

For conditional branches that need more than one trampoline to reach its
target assembler couldn't always find suitable trampoline because
post-loop condition check was placed inside the loop, resulting in
premature loop termination. Move check outside the loop.

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'

2014-11-25  Max Filippov  <jcmvbkbc@gmail.com>

gas/
	* config/tc-xtensa.c (search_trampolines): Move post-loop
	condition check outside the search loop.

gas/testsuite/
	* gas/xtensa/trampoline.d: Add expected output for branches.
	* gas/xtensa/trampoline.s: Add test case for branches.