i965/fs: Extend remove_duplicate_mrf_writes() to handle non-VGRF to MRF copies.
i965/fs: Extend remove_duplicate_mrf_writes() to handle non-VGRF to MRF copies.

Cc: "12.0" <59f39c0db42d4479a46b02d4d2bc11120e37bb44@lists.freedesktop.org>
Reviewed-by: Jason Ekstrand <68c46a606457643eab92053c1c05574abb26f861@jlekstrand.net>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler