Minor derp in dummy_dt function

[GeoZac]

When generating dummy dt, the PRODUCT_MANUFACTURER variable get sets with a minor derp

android_tools/tools/dummy_dt.sh

Line 275 in 483c4b4

printf "\nPRODUCT_MANUFACTURER := "$BRAND"" >> "$DT_DIR"/lineage_"$DEVICE".mk

For instance, in the case of Xiaomi devices, it gets written as
PRODUCT_MANUFACTURER := xiaomi [1]
instead of
PRODUCT_MANUFACTURER := Xiaomi [2]

1. https://github.com/AndroidBlobs/device_xiaomi_surya/blob/46efa22aa8274a6d919961fa2843f831c71c0cce/lineage_surya.mk#L13
2. https://github.com/LineageOS/android_device_xiaomi_surya/blob/4f03c8bd9cd3b51e67b815ea4eaafd8a032e811d/lineage_surya.mk#L31

on other OEMs, incorrect values gets written, eg. OnePlus