nir, ir3: Add option to use unscaled FragCoord for input attachments

nir, ir3: Add option to use unscaled FragCoord for input attachments

When rendering a scaled tile, we need to use the original, hardware
FragCoord when accessing input attachments that are on-tile (i.e. were
rendered to in a previous subpass) because they are also scaled in the
same way that FragCoord is scaled. For input attachments that aren't
already on-tile, however, we need to use the fixed gl_FragCoord. Add a
new intrinsic and a bitfield of input attachments which should use it.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20304>