uuu: make sure usb_otg_path variable is treated as strings

Some specific string were transformed to something else.
Example: usb_otg_path = 2:11 was transfomed as 131 because
being interpreted as a time

etc/dispatcher-config/device-types/base-uboot.jinja2

@@ -261,7 +261,7 @@ actions:
           - "{{ base_uboot_bootcmd }}"
       uuu:
         options:
-          usb_otg_path: {{ uuu_usb_otg_path }}
+          usb_otg_path: "{{ uuu_usb_otg_path }}"
           corrupt_boot_media_command: {{ uuu_corrupt_boot_media_command }}