[Patch, testsuite, avr] Make testcase pass for long source file paths

[Nick Clifton]

Hi Senthil,

>    This trivial patch fixes a test failure that shows up if the source
>    file path is long.

> ld/testsuite/ChangeLog
> 2016-03-17  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>
> 
> 	* ld-avr/gc-section-debugline.d: Relax regex check
>      for CU :.

Approved and applied.

Cheers
  Nick