Boot: Update MCUboot url

MCUboot URL was changed from https://github.com/JuulLabs-OSS/mcuboot
to https://github.com/mcu-tools/mcuboot

Signed-off-by: Tamas Ban <tamas.ban@arm.com>
Change-Id: If5e3d103ed420258046b7cf1071d36bf5e883476
diff --git a/bl2/ext/mcuboot/keys.c b/bl2/ext/mcuboot/keys.c
index ed7665b..53be70a 100644
--- a/bl2/ext/mcuboot/keys.c
+++ b/bl2/ext/mcuboot/keys.c
@@ -19,7 +19,7 @@
 
 /*
  * Original code taken from mcuboot project at:
- * https://github.com/JuulLabs-OSS/mcuboot
+ * https://github.com/mcu-tools/mcuboot
  * Git SHA of the original version: ac55554059147fff718015be9f4bd3108123f50a
  * Modifications are Copyright (c) 2019-2020 Arm Limited.
  */