image: Add support for Plan 9

Signed-off-by: Steven Stallion <sstallion@gmail.com>
Cc: Tom Rini <trini@ti.com>
Reviewed-by: Tom Rini <trini@ti.com>
diff --git a/common/image.c b/common/image.c
index 6afbb40..60c2127 100644
--- a/common/image.c
+++ b/common/image.c
@@ -108,6 +108,7 @@
 #endif
 	{	IH_OS_NETBSD,	"netbsd",	"NetBSD",		},
 	{	IH_OS_OSE,	"ose",		"Enea OSE",		},
+	{	IH_OS_PLAN9,	"plan9",	"Plan 9",		},
 	{	IH_OS_RTEMS,	"rtems",	"RTEMS",		},
 	{	IH_OS_U_BOOT,	"u-boot",	"U-Boot",		},
 #if defined(CONFIG_CMD_ELF) || defined(USE_HOSTCC)