minigbm: consistent style

- Sometimes were return -1 and sometimes -errno.  Prefer -errno
  wherever possible.
- No braces for single line if/else statements.  This does not
  apply gralloc3/gralloc4, since that directory follows AOSP
  style.

BUG=b:178495907
TEST=Cuttlefish CFI

Change-Id: I4c35768e015109730772a972b4b18e8d2c3cbb9b
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/minigbm/+/2665001
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>
Reviewed-by: Jason Macnak <natsu@google.com>
Commit-Queue: Gurchetan Singh <gurchetansingh@chromium.org>
Tested-by: Gurchetan Singh <gurchetansingh@chromium.org>
diff --git a/drv.c b/drv.c
index 78e70d7..cb51887 100644
--- a/drv.c
+++ b/drv.c
@@ -438,9 +438,8 @@
 	/* No CPU access for protected buffers. */
 	assert(!(bo->meta.use_flags & BO_USE_PROTECTED));
 
-	if (bo->is_test_buffer) {
+	if (bo->is_test_buffer)
 		return MAP_FAILED;
-	}
 
 	mapping.rect = *rect;
 	mapping.refcount = 1;
@@ -603,9 +602,8 @@
 	int ret, fd;
 	assert(plane < bo->meta.num_planes);
 
-	if (bo->is_test_buffer) {
+	if (bo->is_test_buffer)
 		return -EINVAL;
-	}
 
 	ret = drmPrimeHandleToFD(bo->drv->fd, bo->handles[plane].u32, DRM_CLOEXEC | DRM_RDWR, &fd);
 
@@ -662,9 +660,8 @@
 	uint32_t count = 0;
 	size_t plane, p;
 
-	if (bo->is_test_buffer) {
+	if (bo->is_test_buffer)
 		return 0;
-	}
 
 	for (plane = 0; plane < bo->meta.num_planes; plane++) {
 		for (p = 0; p < plane; p++)