[testsuite] skip gcc.target/powerpc-tfmode_off.c for eabi

[Mike Stump]

On Jul 8, 2013, at 12:48 PM, Janis Johnson <janis_johnson@mentor.com> wrote:
> Test gcc.target/powerpc-tfmode_off.c fails for powerpc-eabi* targets,
> which do not support TFmode.  This patch skips the test for
> powerpc-*-eabi*.
> 
> OK for mainline and the 4.8 branch?

Ok, but could you please add a comment why it is skipped.  (No TFmode, for example)