tizen: bootscript: vf2: update boot scripts
Update VF2 boot script to match the one developped recently for
LicheePi4A. This improves the following things:
- partitions are discovered by GPT name, not by hardcoded number
- root= kernel parameter is correctly set for partitions up to 19th
- switch to generic devtype/devnum envs like for typical distro_boot case
- reordered some operations and added more comments
- tested A/B booting
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Change-Id: I038f42c8b4f1133798b8d8c8e2f89955b717ca9d