Enable BOARD_PROPERTY_OVERRIDES_SPLIT_ENABLED for full-treble products

BOARD_PROPERTY_OVERRIDES_SPLIT_ENABLED can be true only if early-mount of
partitions is supported. But the early-mount must be supported for full
treble products, and so BOARD_PROPERTY_OVERRIDES_SPLIT_ENABLED should be
set by default for full treble products.

Additionally this CL sets ro.vndk.version regardless of
BOARD_PROPERTY_OVERRIDES_SPLIT_ENABLED.

Bug: 73078796
Test: tested with walleye
Change-Id: Icfe1b6957b55b0f9261d34d7e92db3dc5073cb58