[stdlib] [GPU] Fix address spaces for AMD

The address space values for AMD are incorrect, so adjust the
definitions to be correct for both Nvidia and AMD. Note that there are
some other oddities with address spaces we'll deal with in a follow-up.

MODULAR_ORIG_COMMIT_REV_ID: a9feb989eba84e8cd69242dcd82e6188bb0c8437

stdlib/src/memory/pointer.mojo

@@ -19,6 +19,8 @@ from memory import Pointer
 ```
 """
 
+from sys import is_nvidia_gpu
+
 
 # ===-----------------------------------------------------------------------===#
 # AddressSpace
@@ -36,13 +38,13 @@ struct _GPUAddressSpace(EqualityComparable):
     """Generic address space."""
     alias GLOBAL = AddressSpace(1)
     """Global address space."""
-    alias CONSTANT = AddressSpace(2)
+    alias CONSTANT = AddressSpace(2) if is_nvidia_gpu() else AddressSpace(4)
     """Constant address space."""
     alias SHARED = AddressSpace(3)
     """Shared address space."""
     alias PARAM = AddressSpace(4)
     """Param address space."""
-    alias LOCAL = AddressSpace(5)
+    alias LOCAL = AddressSpace(5) if is_nvidia_gpu() else AddressSpace(3)
     """Local address space."""
 
     @always_inline("nodebug")