gallium: Bump PIPE_MAX_SHADER_IMAGES to 64

This is required by OpenCL

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Karol Herbst <kherbst@redhat.com>
Part-of: <!15988>
175 jobs for !15988 with nir/texture-sampler-info-split in 55 minutes and 37 seconds (queued for 12 seconds)
latest merge request