Fix Legacy GSI settings for BoardConfigGsiCommon.mk

Legacy GSI had been changed to include BoardConfigGsiCommon.mk
instead of treble_common*.mk. However, some default settings are
different than the original. This patch fixes
BOARD_BUILD_SYSTEM_ROOT_IMAGE in Legacy GSI makefiles.

The patch also removes redundant settings and fix some comments.

Bug: 122282239
Test: make
Change-Id: Ie4eb8cf410bfd2edc74648c0e5ee81028242a1b7
diff --git a/target/board/BoardConfigGsiCommon.mk b/target/board/BoardConfigGsiCommon.mk
index a853b3c..f9e9ee1 100644
--- a/target/board/BoardConfigGsiCommon.mk
+++ b/target/board/BoardConfigGsiCommon.mk
@@ -25,9 +25,13 @@
 # Enable dynamic system image size and reserved 64MB in it.
 BOARD_SYSTEMIMAGE_PARTITION_RESERVED_SIZE := 67108864
 
-# Generic AOSP image always requires separate vendor.img
+# GSI always requires separate vendor packages to vendor.img
 TARGET_COPY_OUT_VENDOR := vendor
 
+# Creates metadata partition mount point under root for
+# the devices with metadata parition
+BOARD_USES_METADATA_PARTITION := true
+
 # Android Verified Boot (AVB):
 #   Set AVB_VBMETA_IMAGE_FLAGS_VERIFICATION_DISABLED (--flag 2) in
 #   vbmeta.img to disable AVB verification.
@@ -43,15 +47,13 @@
 BOARD_AVB_SYSTEM_ROLLBACK_INDEX := $(PLATFORM_SECURITY_PATCH_TIMESTAMP)
 BOARD_AVB_SYSTEM_ROLLBACK_INDEX_LOCATION := 1
 
+# GSI specific System Properties
 ifneq (,$(filter userdebug eng,$(TARGET_BUILD_VARIANT)))
 # GSI is always userdebug and needs a couple of properties taking precedence
 # over those set by the vendor.
 TARGET_SYSTEM_PROP := build/make/target/board/gsi_system.prop
 endif
 
-# Android generic system image always create metadata partition
-BOARD_USES_METADATA_PARTITION := true
-
 # Set this to create /cache mount point for non-A/B devices that mounts /cache.
 # The partition size doesn't matter, just to make build pass.
 BOARD_CACHEIMAGE_FILE_SYSTEM_TYPE := ext4