minigbm: use int instead of size_t for plane index

Rationale: this will help get Rust gbm bindings into Android
(go/drm-gbm-rust-crates-for-android) without needing minigbm-specific
patches to upstream Rust code.

Mesa gbm defines the plane argument for some functions as int rather
than size_t. While this doesn't bother C/C++ compilers too much,
attempting to use bindgen-generated Rust bindings to minigbm with gbm
Rust crate[1] fails.

[1] https://crates.io/crates/gbm

Bug: 328363177
Test: cros build-packages --board=amd64-generic minigbm drm-tests
Change-Id: I5938633e0936bf1b9aafb856bfb966ceb1fb1a2b
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/minigbm/+/5352370
Reviewed-by: Dominik Behr <dbehr@chromium.org>
Commit-Queue: Marcin Radomski <dextero@google.com>
Tested-by: Marcin Radomski <dextero@google.com>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>
2 files changed