Revert "render/drm_format_set: remove special LINEAR case"

This reverts commit 6d281d96cb.

render/drm_format_set.c

@@ -144,6 +144,18 @@ struct wlr_drm_format *wlr_drm_format_intersect(
 		const struct wlr_drm_format *a, const struct wlr_drm_format *b) {
 	assert(a->format == b->format);
 
+	// Special case: if a format only supports LINEAR and the other supports
+	// implicit modifiers, force LINEAR. This will force the allocator to
+	// create a buffer with a linear layout instead of an implicit modifier.
+	if (a->len == 1 && a->modifiers[0] == DRM_FORMAT_MOD_LINEAR &&
+			wlr_drm_format_has(b, DRM_FORMAT_MOD_INVALID)) {
+		return wlr_drm_format_dup(a);
+	}
+	if (b->len == 1 && b->modifiers[0] == DRM_FORMAT_MOD_LINEAR &&
+			wlr_drm_format_has(a, DRM_FORMAT_MOD_INVALID)) {
+		return wlr_drm_format_dup(b);
+	}
+
 	size_t format_cap = a->len < b->len ? a->len : b->len;
 	size_t format_size = sizeof(struct wlr_drm_format) +
 		format_cap * sizeof(a->modifiers[0]);