docs: cpu -> CPU

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/29879>

docs/drivers/asahi.rst

@@ -342,7 +342,7 @@ concepts used in PowerVR GPUs appear in AGX.
 
    USC
    Unified Shader Cores
-      A unified shader core is a small cpu that runs shader code. The core is
+      A unified shader core is a small CPU that runs shader code. The core is
       unified because a single ISA is used for vertex, pixel and compute
       shaders. This differs from older GPUs where the vertex, fragment and
       compute have separate ISAs for shader stages.