softpipe: dynamically allocate space for immediate constants

softpipe: dynamically allocate space for immediate constants

The number of immediate constants was fixed and the size check was
only done by means of an assertion. Given this a shader that emits
more immediate constants would result in a memory corruption when
mesa is build in release mode.

Instead of using this fixed limit allocate the space dynamically, let it
grow as needed, and also remove the unused ImmArray.

Fixes: dEQP-GLES31.functional.ssbo.layout.random.arrays_of_arrays.1
Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Reviewed-by: Roland Scheidegger <sroland@vmware.com>