Remove byte slice downcasts in CpuBinding

All downcasts are to typed objects.

src/cpu_dispatch.rs

diff --git a/src/cpu_dispatch.rs b/src/cpu_dispatch.rs
index fa1bbeb..2c3409c 100644
--- a/src/cpu_dispatch.rs
+++ b/src/cpu_dispatch.rs
@@ -18,22 +18,6 @@
     Texture(&'a CpuTexture),
 }
 
-pub enum CpuBufGuard<'a> {
-    Slice(&'a [u8]),
-    Interior(RefMut<'a, Vec<u8>>),
-}
-
-impl<'a> Deref for CpuBufGuard<'a> {
-    type Target = [u8];
-
-    fn deref(&self) -> &Self::Target {
-        match self {
-            CpuBufGuard::Slice(s) => s,
-            CpuBufGuard::Interior(r) => r,
-        }
-    }
-}
-
 pub enum TypedBufGuard<'a, T: ?Sized> {
     Slice(&'a T),
     Interior(Ref<'a, T>),
@@ -75,27 +59,7 @@
     }
 }
 
-impl<'a> CpuBufGuard<'a> {
-    /// Get a mutable reference to the buffer.
-    ///
-    /// Panics if the underlying resource is read-only.
-    pub fn as_mut(&mut self) -> &mut [u8] {
-        match self {
-            CpuBufGuard::Interior(r) => &mut *r,
-            _ => panic!("tried to borrow immutable buffer as mutable"),
-        }
-    }
-}
-
 impl<'a> CpuBinding<'a> {
-    pub fn as_buf(&self) -> CpuBufGuard {
-        match self {
-            CpuBinding::Buffer(b) => CpuBufGuard::Slice(b),
-            CpuBinding::BufferRW(b) => CpuBufGuard::Interior(b.borrow_mut()),
-            _ => panic!("resource type mismatch"),
-        }
-    }
-
     pub fn as_typed<T: Pod>(&self) -> TypedBufGuard<T> {
         match self {
             CpuBinding::Buffer(b) => TypedBufGuard::Slice(bytemuck::from_bytes(b)),