radv: allocate enough space in cmdbuf when starting a subpass

This fixes some CTS crashes with:
dEQP-VK.renderpass2.suballocation.attachment_write_mask.attachment_count_8.start_index_*

Ideally, we should check cmd_buffer->cs->max_dw because there is
likely enough space (the internal clear draws allocate space), but
keep that way for consistency.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>

src/amd/vulkan/radv_cmd_buffer.c

@@ -3446,7 +3446,7 @@ radv_cmd_buffer_begin_subpass(struct radv_cmd_buffer *cmd_buffer,
 	struct radv_subpass *subpass = &state->pass->subpasses[subpass_id];
 
 	MAYBE_UNUSED unsigned cdw_max = radeon_check_space(cmd_buffer->device->ws,
-							   cmd_buffer->cs, 2048);
+							   cmd_buffer->cs, 4096);
 
 	radv_subpass_barrier(cmd_buffer, &subpass->start_barrier);