nil: Drop the nil_extent/offset4d() helpers

They're only used one place each in NVK and we can just use a struct
initializer instead.

Reviewed-by: Lina Versace <linyaa@google.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28639>

src/nouveau/nil/extent.rs

@@ -15,21 +15,6 @@ pub struct Extent4D {
     pub array_len: u32,
 }
 
-#[no_mangle]
-pub extern "C" fn nil_extent4d(
-    width: u32,
-    height: u32,
-    depth: u32,
-    array_len: u32,
-) -> Extent4D {
-    Extent4D {
-        width,
-        height,
-        depth,
-        array_len,
-    }
-}
-
 impl Extent4D {
     pub fn new(
         width: u32,
@@ -145,11 +130,6 @@ pub struct Offset4D {
     pub a: u32,
 }
 
-#[no_mangle]
-pub extern "C" fn nil_offset4d(x: u32, y: u32, z: u32, a: u32) -> Offset4D {
-    Offset4D { x, y, z, a }
-}
-
 impl Offset4D {
     fn div_floor(self, other: Extent4D) -> Self {
         Self {

src/nouveau/vulkan/nvk_cmd_copy.c

@@ -68,13 +68,23 @@ nouveau_copy_rect_buffer(struct nvk_buffer *buf,
 static struct nil_offset4d
 vk_to_nil_offset(VkOffset3D offset, uint32_t base_array_layer)
 {
-   return nil_offset4d(offset.x, offset.y, offset.z, base_array_layer);
+   return (struct nil_offset4d) {
+      .x = offset.x,
+      .y = offset.y,
+      .z = offset.z,
+      .a = base_array_layer
+   };
 }
 
 static struct nil_extent4d
 vk_to_nil_extent(VkExtent3D extent, uint32_t array_layers)
 {
-   return nil_extent4d(extent.width, extent.height, extent.depth, array_layers);
+   return (struct nil_extent4d) {
+      .width      = extent.width,
+      .height     = extent.height,
+      .depth      = extent.depth,
+      .array_len  = array_layers,
+   };
 }
 
 static struct nouveau_copy_buffer