gtowifi: move to 21

Change-Id: I0696db5d2adcc968b44a609bf50d493819d67a2a

_data/devices/gtowifi.yml

@@ -9,7 +9,7 @@ codename: gtowifi
 cpu: Cortex-A53
 cpu_cores: '4'
 cpu_freq: 4 x 2.0 GHz
-current_branch: 20
+current_branch: 21
 dimensions: {depth: 8, height: 210, width: 124.4}
 download_boot: With the device powered off, plug in the device while holding <kbd>Volume up</kbd> + <kbd>Volume Down</kbd> + <kbd>Power</kbd>.
 firmware_update: firmware_update_samsung_gtowifi
@@ -35,5 +35,5 @@ tree: android_device_samsung_gtowifi
 type: tablet
 vendor: Samsung
 vendor_short: samsung
-versions: [20]
+versions: [20, 21]
 wifi: 802.11 a/b/g/n