image: Add a name for invalid types

At present the name is NULL, which prevents qsort() fromp being used. Use
the name "invalid" instead.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/common/image.c b/common/image.c
index 4e503b3..e9095f4 100644
--- a/common/image.c
+++ b/common/image.c
@@ -69,7 +69,7 @@
 #endif
 
 static const table_entry_t uimage_arch[] = {
-	{	IH_ARCH_INVALID,	NULL,		"Invalid ARCH",	},
+	{	IH_ARCH_INVALID,	"invalid",	"Invalid ARCH",	},
 	{	IH_ARCH_ALPHA,		"alpha",	"Alpha",	},
 	{	IH_ARCH_ARM,		"arm",		"ARM",		},
 	{	IH_ARCH_I386,		"x86",		"Intel x86",	},
@@ -97,7 +97,7 @@
 };
 
 static const table_entry_t uimage_os[] = {
-	{	IH_OS_INVALID,	NULL,		"Invalid OS",		},
+	{	IH_OS_INVALID,	"invalid",	"Invalid OS",		},
 	{	IH_OS_LINUX,	"linux",	"Linux",		},
 #if defined(CONFIG_LYNXKDI) || defined(USE_HOSTCC)
 	{	IH_OS_LYNXOS,	"lynxos",	"LynxOS",		},
@@ -144,7 +144,7 @@
 	{	IH_TYPE_KERNEL_NOLOAD, "kernel_noload",  "Kernel Image (no loading done)", },
 	{	IH_TYPE_KWBIMAGE,   "kwbimage",   "Kirkwood Boot Image",},
 	{	IH_TYPE_IMXIMAGE,   "imximage",   "Freescale i.MX Boot Image",},
-	{	IH_TYPE_INVALID,    NULL,	  "Invalid Image",	},
+	{	IH_TYPE_INVALID,    "invalid",	  "Invalid Image",	},
 	{	IH_TYPE_MULTI,	    "multi",	  "Multi-File Image",	},
 	{	IH_TYPE_OMAPIMAGE,  "omapimage",  "TI OMAP SPL With GP CH",},
 	{	IH_TYPE_PBLIMAGE,   "pblimage",   "Freescale PBL Boot Image",},