Fix overlapping GPU device bitmasks

This did not end up affecting actual behavior, but it is wrong.
Found by Ethan Hall.

Ref D14525

source/blender/gpu/GPU_platform.h

@@ -25,9 +25,9 @@ typedef enum eGPUDeviceType {
   GPU_DEVICE_ATI = (1 << 1),
   GPU_DEVICE_INTEL = (1 << 2),
   GPU_DEVICE_INTEL_UHD = (1 << 3),
-  GPU_DEVICE_APPLE = (1 << 3),
-  GPU_DEVICE_SOFTWARE = (1 << 4),
-  GPU_DEVICE_UNKNOWN = (1 << 5),
+  GPU_DEVICE_APPLE = (1 << 4),
+  GPU_DEVICE_SOFTWARE = (1 << 5),
+  GPU_DEVICE_UNKNOWN = (1 << 6),
   GPU_DEVICE_ANY = (0xff),
 } eGPUDeviceType;