panfrost: fixup typo in 16x sample-pattern

This is an n-queen pattern, where no two values should be on the same
row or column. But this and the second to last element has the same y
component, and neither has the negative one.

Let's fix this up by setting the first value to the negative value. This
matches the D3D 16x sample pattern.

Fixes: a61fb62966 ("panfrost: Upload sample positions on device init")
Reviewed-by: Lars-Ivar Hesselberg Simonsen <lars-ivar.simonsen@arm.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/33925>

src/panfrost/lib/pan_samples.c

@@ -115,7 +115,7 @@ const struct mali_sample_positions sample_position_lut[] = {
          SAMPLE16( 5,  3),
          SAMPLE16( 3, -5),
          SAMPLE16(-2,  6),
-         SAMPLE16( 0,  7),
+         SAMPLE16( 0, -7),
          SAMPLE16(-4, -6),
          SAMPLE16(-6,  4),
          SAMPLE16(-8,  0),