platform: partition_parser: Add get_partition_count()/get_partition_entries()

Mostly from commit e358f1f9c2697022f7f4d496df514ba9df5f71a1
("platform: msm_shared: a/b support, update partition index lookup.").

(cherry-picked from https://github.com/msm8916-mainline/lk2nd/commit/fdf7bada77aa1e84dfb99aab5f4ba66530b129f8)

Issue: FP2P-433
Change-Id: Ibfb6afd1ee84f8a28d6538c8cc63ee8bcccda884
2 files changed