r600g/sb: Update last_cf for loops
r600g/sb: Update last_cf for loops

CF_END could end up emitted in the middle of a shader on cayman
when there was a loop at the very end.

Fixes glsl-1.50-geometry-end-primitive and
ext_transform_feedback-geometry-shaders-basic piglit tests.

Signed-off-by: Glenn Kennard <feea5431f8695a3af7470d472cb16ac8e02bab01@gmail.com>
Signed-off-by: Dave Airlie <f2295d84e358395675bc8031be58672073ae065e@redhat.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler