i965/fs: Create a has_side_effects for fs_inst

i965/fs: Create a has_side_effects for fs_inst

When an instruction has a side effect, it impacts the available options when
reordering an instruction. As the EOT flag is an implied write to the render
target in the FS, it can be considered a side effect.

This patch shouldn't actually have any impact on the current code since the EOT
flag implies that the opcode is already one with side effects,
FS_OPCODE_FB_WRITE. The next patch however will introduce an optimization
whereby the EOT flag can occur with an opcode SHADER_OPCODE_TEX, and as that
instruction will perform the same implied write to the render target, it cannot
be reordered.

v2: Remove extra whitespace (Matt)

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>