util: Add a way to set the min_buffer_size in linear_alloc

The default value remains 2048, which is also used for rounding up
any user provided size.

The option is useful in cases where there's a better idea of the
amount of data that's going to be used.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/25279>

src/util/ralloc.h

@@ -579,6 +579,10 @@ typedef struct linear_ctx linear_ctx;
  */
 void *linear_alloc_child(linear_ctx *ctx, unsigned size);
 
+typedef struct {
+   unsigned min_buffer_size;
+} linear_opts;
+
 /**
  * Allocate a linear context that will internally hold linear buffers.
  * Use it for all child node allocations.
@@ -587,6 +591,8 @@ void *linear_alloc_child(linear_ctx *ctx, unsigned size);
  */
 linear_ctx *linear_context(void *ralloc_ctx);
 
+linear_ctx *linear_context_with_opts(void *ralloc_ctx, const linear_opts *opts);
+
 /**
  * Same as linear_alloc_child, but also clears memory.
  */