MIPS: ath79: Add a machine entry for booting OF machines

As I'm using a board with a broken old bootloader I hardcoded the
mips_machtype and did't notice that the machine entry was still
missing.

[ralf@linux-mips.org: Fixed spelling message noticed by Sergei Shtylyov
<sergei.shtylyov@cogentembedded.com>.]
Signed-off-by: Alban Bedel <albeu@free.fr>
Cc: Qais Yousef <qais.yousef@imgtec.com>
Cc: Felix Fietkau <nbd@openwrt.org>
Cc: Andrew Bresticker <abrestic@chromium.org>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/11503/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/ath79/setup.c

@@ -281,3 +281,8 @@ MIPS_MACHINE(ATH79_MACH_GENERIC,
 	     "Generic",
 	     "Generic AR71XX/AR724X/AR913X based board",
 	     ath79_generic_init);
+
+MIPS_MACHINE(ATH79_MACH_GENERIC_OF,
+	     "DTB",
+	     "Generic AR71XX/AR724X/AR913X based board (DT)",
+	     NULL);