cmd: Add 2048 game

Add the 2048 game, a good demo of ANSI sequences and a way to waste a
little time.

Bring it it from Barebox, modified for code style.

Signed-off-by: Simon Glass <sjg@chromium.org>

cmd/Makefile

@@ -12,6 +12,7 @@ obj-y += panic.o
 obj-y += version.o
 
 # command
+obj-$(CONFIG_CMD_2048) += 2048.o
 obj-$(CONFIG_CMD_ACPI) += acpi.o
 obj-$(CONFIG_CMD_ADDRMAP) += addrmap.o
 obj-$(CONFIG_CMD_AES) += aes.o