gallium: normalized_coords -> unnormalized_coords

A lot of code zero-initializes pipe_sampler_state, and sets the states the non-zero fields manually. This means that normalized_coords is the "default" setting.

However, setting normalized_coords to true isn't allways allowed, and we'd need to check PIPE_CAP_TEXRECT first. So it's not really the ideal default here. There's recently been found quite a bit of bugs in this area, where the state-tracker didn't properly lower texrects.

Let's switch this around to avoid more bugs like this in the future.