Don't override BOARD_SEPOLICY_VERS if already set.

Allow the input manifest to already contain BOARD_SEPOLICY_VERS.

Bug: 78943004 # for full combine
Test: m assembled_framework_manifest.xml produces correct manifest w/o
    warning + w/o overriding sepolicy vers.

Change-Id: Ieb98d8a650fb8f5791f08e378514d3f8f04f131f
1 file changed