pvr: Don't override commands copied to new buffer when extending cs

The next pointer wasn't advanced past the start of the new buffer,
meaning anything overflowed into the new buffer would be overwritten
on the next emit.

Signed-off-by: Matt Coster <matt.coster@imgtec.com>
Reviewed-by: Luigi Santivetti <luigi.santivetti@imgtec.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24692>

src/imagination/vulkan/pvr_csb.c

@@ -232,6 +232,7 @@ static bool pvr_csb_buffer_extend(struct pvr_csb *csb)
       stream_link_space + PVRX(VDMCTRL_GUARD_SIZE_DEFAULT);
    const uint32_t cache_line_size =
       rogue_get_slc_cache_line_size(&csb->device->pdevice->dev_info);
+   size_t current_state_update_size = 0;
    struct pvr_bo *pvr_bo;
    VkResult result;
 
@@ -260,7 +261,7 @@ static bool pvr_csb_buffer_extend(struct pvr_csb *csb)
 
    /* if this is not the first BO in csb */
    if (csb->pvr_bo) {
-      const size_t current_state_update_size =
+      current_state_update_size =
          (uint8_t *)csb->next - (uint8_t *)csb->relocation_mark;
       void *new_buffer = pvr_bo->bo->map;
 
@@ -291,7 +292,7 @@ static bool pvr_csb_buffer_extend(struct pvr_csb *csb)
     * sure we don't run out of space when a stream link is required.
     */
    csb->end = csb->start + pvr_bo->bo->size - stream_reserved_space;
-   csb->next = csb->start;
+   csb->next = csb->start + current_state_update_size;
 
    list_addtail(&pvr_bo->link, &csb->pvr_bo_list);