[U-Boot] [PATCH] mkimage: fix display of image types list

[Baruch Siach]

Since commit 5b9d44df2307f (mkimage: Display a better list of available image
types) mkimage usage text suggest to "use -T to see a list of available image
types". Unfortunately, commit 02221f29deb8 (mkimage: Convert to use getopt())
broke that feature, because getopt() fails when -T has no option argument.

Make the -T option argument optional to restore the original behaviour.

Cc: Simon Glass <sjg at chromium.org>
Signed-off-by: Baruch Siach <baruch at tkos.co.il>
---
 tools/mkimage.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/tools/mkimage.c b/tools/mkimage.c
index d982bc5665f1..2c7801e8f836 100644
--- a/tools/mkimage.c
+++ b/tools/mkimage.c
@@ -144,7 +144,7 @@ static void process_args(int argc, char **argv)
 	int opt;
 
 	while ((opt = getopt(argc, argv,
-			     "a:A:b:c:C:d:D:e:Ef:Fk:i:K:ln:N:p:O:rR:qsT:vVx")) != -1) {
+			     "a:A:b:c:C:d:D:e:Ef:Fk:i:K:ln:N:p:O:rR:qsT::vVx")) != -1) {
 		switch (opt) {
 		case 'a':
 			params.addr = strtoull(optarg, &ptr, 16);
@@ -260,8 +260,9 @@ static void process_args(int argc, char **argv)
 			params.skipcpy = 1;
 			break;
 		case 'T':
-			type = genimg_get_type_id(optarg);
-			if (type < 0) {
+			if (optarg)
+				type = genimg_get_type_id(optarg);
+			if (optarg == NULL || type < 0) {
 				show_valid_options(IH_TYPE);
 				usage("Invalid image type");
 			}
-- 
2.11.0