Switch pixel format loss fields to number of bits

This makes more sense and handles pixel formats with > 8 bits per channel

Fixes https://github.com/libsdl-org/SDL/issues/10168

include/SDL3/SDL_pixels.h

@@ -751,10 +751,10 @@ typedef struct SDL_PixelFormat
     Uint32 Gmask;
     Uint32 Bmask;
     Uint32 Amask;
-    Uint8 Rloss;
-    Uint8 Gloss;
-    Uint8 Bloss;
-    Uint8 Aloss;
+    Uint8 Rbits;
+    Uint8 Gbits;
+    Uint8 Bbits;
+    Uint8 Abits;
     Uint8 Rshift;
     Uint8 Gshift;
     Uint8 Bshift;