README: sort MACHINE names

Previously the MACHINEs were listed in the order in which they were added to
the layer. Going forward, separate the list into 32 vs 64 bit, sort each of
those groups, while distinguishing between which boards support wic and which
don't.

Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>
Signed-off-by: Trevor Woerner <twoerner@gmail.com>

README

@@ -18,34 +18,39 @@ Dependencies:
 Status of supported boards:
 --------------------------
 	builds and boots wic image:
-		nanopi-m4
-		nanopi-m4-2gb
-		rock-pi-e
-		rock-pi-4a
-		rock-pi-4b
-		rock-pi-4c
-		rock64
-		tinker-board
-		tinker-board-s
-		vyasa-rk3288
-		firefly-rk3288
-		nanopi-r4s
-		rock-5b
-		nanopi-r2s
-		nanopi-m4b
-		rock-pi-s
-		rock-5a
-		roc-rk3328-cc
-		roc-rk3308-cc
-		orangepi-5-plus
-		rock-3a
-		rock-4c-plus
-		radxa-zero-3e
-		radxa-zero-3w
+		32-bit:
+			firefly-rk3288
+			tinker-board
+			tinker-board-s
+			vyasa-rk3288
+
+		64-bit:
+			nanopi-m4
+			nanopi-m4-2gb
+			nanopi-m4b
+			nanopi-r2s
+			nanopi-r4s
+			orangepi-5-plus
+			radxa-zero-3e
+			radxa-zero-3w
+			roc-rk3308-cc
+			roc-rk3328-cc
+			rock-3a
+			rock-4c-plus
+			rock-5a
+			rock-5b
+			rock-pi-4a
+			rock-pi-4b
+			rock-pi-4c
+			rock-pi-e
+			rock-pi-s
+			rock64
+
 	builds:
-		marsboard-rk3066
-		radxarock
-		rock2-square
+		32-bit:
+			marsboard-rk3066
+			radxarock
+			rock2-square
 
 Notes:
 -----