cargo-c-native: convert from git fetcher to crate fetcher

cargo-c-native: convert from git fetcher to crate fetcher

Fetching from git requires manually maintaining Cargo.lock
which is tedious and unclear how to do correctly,
especially with version updates. On the other hand, crates
do include Cargo.lock, and this way the revisions would match
upstream's and crate users (which requires regenerating
crates.inc to match the lock file).

Signed-off-by: Alexander Kanavin <alex@linutronix.de>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>