Add sepolicy for system_ext partition

Bug: 134359158
Bug: 137083818
Test: build and flash; check if /system_ext is not empty
Change-Id: I9a068956e45ddd8edcab3b7e0c34e6451b010932
diff --git a/vendor/qcom/sdm845/file_contexts b/vendor/qcom/sdm845/file_contexts
index 4603b8d..e4de34e 100644
--- a/vendor/qcom/sdm845/file_contexts
+++ b/vendor/qcom/sdm845/file_contexts
@@ -30,6 +30,7 @@
 /dev/block/platform/soc/1d84000\.ufshc/by-name/persist         u:object_r:persist_block_device:s0
 /dev/block/platform/soc/1d84000\.ufshc/by-name/product_[ab]    u:object_r:system_block_device:s0
 /dev/block/platform/soc/1d84000\.ufshc/by-name/system_[ab]     u:object_r:system_block_device:s0
+/dev/block/platform/soc/1d84000\.ufshc/by-name/system_ext_[ab] u:object_r:system_block_device:s0
 /dev/block/platform/soc/1d84000\.ufshc/by-name/vendor_[ab]     u:object_r:system_block_device:s0
 /dev/block/platform/soc/1d84000\.ufshc/by-name/userdata        u:object_r:userdata_block_device:s0
 /dev/block/platform/soc/1d84000\.ufshc/by-name/xbl_[ab]        u:object_r:xbl_block_device:s0