radeonsi: allocate the array of immediates dynamically

radeonsi: allocate the array of immediates dynamically

Currently, we can store up to 256 immediates in a static array,
but this is not always enough. Instead, allocate a dynamic array
like what we currently do for temps.

This fixes a segfault with
dEQP-GLES31.functional.ssbo.layout.random.all_shared_buffer.23

No regressions found with full piglit run.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>