xiaomi-sagit: new device (Xiaomi Mi 6)

Will be usable after [https://gitlab.com/msm8998-mainline/linux/-/merge_requests/1 linux PR merged] and corresponding package updated

.ci/testcases/test_firmware.py

@@ -17,6 +17,7 @@ def test_aports_firmware(args):
     excluded = [
         "firmware-motorola-potter",  # Depends on soc-qcom-msm8916-ucm
         "firmware-oneplus-msm8998",  # Depends on soc-qcom-sdm845-nonfree-firmware
+        "firmware-xiaomi-sagit",  # Depends on soc-qcom-sdm845-nonfree-firmware
         "firmware-samsung-baffinlite",  # Depends on firmware-aosp-broadcom-wlan
         "firmware-samsung-crespo",  # Depends on firmware-aosp-broadcom-wlan
         "firmware-samsung-maguro",  # Depends on firmware-aosp-broadcom-wlan