i965: Ignore reloc read/write domains

i965: Ignore reloc read/write domains

Since before the kernel supported I915_EXEC_NO_RELOC, long before our
minimum kernel requirement, the kernel unconditionally invalidated all
GPU TLBs before a batch and flushed all GPU caches after a batch. At
that moment, the only use for read/write domain was for activity
tracking, ensuring that future reads waited for the last writer and
future writes waited for all reads. This only requires a single bit in
the execbuf interface which can be supplied via the NO_RELOC interface,
making the use of relocation domains entirely redundant.

Trimming the excess writes into the array allows the compiler to be much
more frugal:

   text	   data	    bss	    dec	    hex	filename
8493790	 357184	 424944	9275918	 8d8a0e	i965_dri.baseline
8493758	 357184	 424944	9275886	 8d89ee	i965_dri.so

(This text improvement really does come from dropping domains, not from
the new use of C99 initializers.)

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>