linuxkpi: Add <linux/linux_logo.h>

It only defines the `struct linux_logo` structure for now. It does not
define any actual logo.

Reviewed by:	bz, emaste
Sponsored by:	The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D55735

sys/compat/linuxkpi/common/include/linux/linux_logo.h

@@ -0,0 +1,19 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2026 The FreeBSD Foundation
+ */
+
+#ifndef	_LINUXKPI_LINUX_LINUX_LOGO_H_
+#define	_LINUXKPI_LINUX_LINUX_LOGO_H_
+
+struct linux_logo {
+	int			 type;
+	unsigned int		 width;
+	unsigned int		 height;
+	unsigned int		 clutsize;
+	const unsigned char 	*clut;
+	const unsigned char 	*data;
+};
+
+#endif /* _LINUXKPI_LINUX_LINUX_LOGO_H_ */