begonia: Set Redmi as PRODUCT_BRAND

The Redmi Note 8 Pro (begonia) is the first smartphone with Redmi as PRODUCT_BRAND
(https://github.com/AndroidDumps/redmi_begonia_dump/blob/begonia-user-9-PPR1.180610.011-V10.4.11.0.PGGCNXM-release-keys/system/system/build.prop#L24)

Change-Id: Idc7d4b404f490a6f6cbc4e3f07a3ce85d295a906

omni_begonia.mk

@@ -25,7 +25,7 @@ $(call inherit-product, vendor/omni/config/common.mk)
 ## Device identifier. This must come after all inclusions
 PRODUCT_DEVICE := begonia
 PRODUCT_NAME := omni_begonia
-PRODUCT_BRAND := Xiaomi
+PRODUCT_BRAND := Redmi
 PRODUCT_MODEL := Redmi Note 8 Pro
 PRODUCT_MANUFACTURER := Xiaomi