util/list: add list_first/last_entry
util/list: add list_first/last_entry

I need an easier way to get at head/tail in ir3.

Signed-off-by: Rob Clark <6f78cdb10adbe0a7fbbf4098125a51f401c77a5f@freedesktop.org>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler