commit 61fd888a7f4d741714553f36839dd49fb0065731
author Fabio Utzig <utzig@apache.org> Sat Sep 14 20:00:20 2019 -0300
committer Fabio Utzig <utzig@utzig.org> Wed Sep 18 07:38:50 2019 -0500
tree 4a46b67badf37666eb1075259fe298ec52e54644
parent 4f0ea747c314547daa6b6299ccbd77ae4dee6758

Add TLV iterator API

This introduces an API which allows for iteration over an image's TLVs
without resorting to low-level implementation details. All previous TLV
low-level handling was updated to comply with this new interface, and it
also makes it easier for external code to handle TLVs.

The API provides two functions:

1) To start a new iterator:

```
int bootutil_tlv_iter_begin(struct image_tlv_iter *it,
                            const struct image_header *hdr,
                            const struct flash_area *fap, uint8_t type,
                            bool prot);
```

2) To iterate over existing TLVs of given type:

```
int bootutil_tlv_iter_next(struct image_tlv_iter *it, uint32_t *off,
                           uint16_t *len, uint8_t *type);
```

A type of IMAGE_TLV_ANY was added to allow for iteration over all TLVs.

Low-level TLV access functions were removed from API, but low-level
structs are still visible in the namespace.

Signed-off-by: Fabio Utzig <utzig@apache.org>