gpt: allow spaces in partition list

This allows spliting partition list to several lines in environment file

ex:
--------------------
gpt_partition_list=
	name=boot1,size=5MiB,start=0x100000;
	name=boot2,size=5MiB;
	name=rootfs1,size=70MiB;
	name=rootfs2,size=70MiB;
	name=overlay1,size=20MiB;
	name=overlay2,size=20MiB;
	name=art,size=4MiB;

Signed-off-by: Mikhail Kshevetskiy <mikhail.kshevetskiy@iopsys.eu>
Reviewed-by: Sam Protsenko <semen.protsenko@linaro.org>
Tested-by: Sam Protsenko <semen.protsenko@linaro.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/cmd/gpt.c b/cmd/gpt.c
index aeabd19..86b7701 100644
--- a/cmd/gpt.c
+++ b/cmd/gpt.c
@@ -116,6 +116,7 @@
 		k = strsep(&v, "=");
 		if (!k)
 			break;
+		k += strspn(k, " \t");
 		if  (strcmp(k, key) == 0) {
 			new = strdup(v);
 			break;
@@ -150,6 +151,7 @@
 		k = strsep(&s, ",");
 		if (!k)
 			break;
+		k += strspn(k, " \t");
 		if  (strcmp(k, key) == 0) {
 			result = true;
 			break;