fix bindgen installation instruction
fix bindgen installation instruction

The bindgen cli tool has changed to a workspace member of rust-bindegen
repo: https://github.com/rust-lang/rust-bindgen/commits/master/bindgen-cli

Change-Id: Ie3248d61919fdb742e49f57a10f5db827cd8230d
Signed-off-by: Eval EXEC <27590d0c2340660404e67a1db0622203e88ac8a1@gmail.com>
Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/3964808
Reviewed-by: Dennis Kempin <cd09796fb571bec2782819dbfd33307f65b1c778@google.com>
Commit-Queue: Dennis Kempin <cd09796fb571bec2782819dbfd33307f65b1c778@google.com>

google/crosvm,google/crosvm,google/crosvm,google/crosvm