[U-Boot] [PATCHv2 0/3] spl: Lightweight UBI and UBI fastmap support

This is an update of Thomas's patchset: https://patchwork.ozlabs.org/patch/367305/ https://patchwork.ozlabs.org/patch/367306/

Changes from previous version: - fixes ubi_calc_fm_size to include also sizeof(struct ubi_fm_sb) - dropped private copy of ubi-media.h - ubi-wrapper.h now contains only needed definitions from ubi.h and ubi-user.h - used return values from errno.h - added example implementation for igep00x0.