gcc: Drop libgfortran patch

As far as I can see, when building libgfortran we don't set GFORTRAN so this
patch does nothing any more. The fortran build and gcc recipes have changed
massively since gcc 4.2.2 so I think this patch is simply obsolete.

I did test building libgfortran with and without this patch and there was
no difference, the correct fortran compiler is found. If it were an issue
we should just set GFORTRAN correctly. Therefore drop the patch.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>