OTA_SIZE_UNKNOWN is u32 while esp_ota_begin now wants usize

[faern]

In esp-idf-sys 0.32.0 the argument image_size of esp_ota_begin became a usize rather than a u32. But the constant OTA_SIZE_UNKNOWN is still a u32. This means that the place where the constant is supposed to be used, it's not compatible. I can of course just cast it, but it would be more ergonomic if they had the same types.

[ivmarkov]

esp-idf-sys is really just raw bindings. Specifically OTA_SIZE_UKNOWN is probably a #define and as such the Rust bindgen utility does not really know its type, and arbitrary defines these as either i32 and u32.

Under some special circumstances, we can force bindgen - for selected C macros - to derive a different type, but this is a manual effort for each such constant, and as such, we only do it for constants which are used very often. I don't think OTA_SIZE_UNKNOWN can be justified to fall into this category.