v3d: Mark scheduling dependency for prim id and first output

v3d: Mark scheduling dependency for prim id and first output

The input primitive ID is read from the VPM in the same memory segment
as the outputs. This means that writing the GS header to VPM location 0
needs to be done after reading the primitive ID. This patch adds a
dependency between the load_primitive_id intrinsic and the store_output
intrinsic for location 0 to stop the scheduler from reordering them.

v2: Use an enum for the dependency class number.
v3: Add "GS" to the class enum name.

Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5953>