[build] Remove long-obsolete header file

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/ipxe/linux_compat.h

@@ -1,27 +0,0 @@
-#ifndef _IPXE_LINUX_COMPAT_H
-#define _IPXE_LINUX_COMPAT_H
-
-/** @file
- *
- * Linux code compatibility
- *
- * This file exists to ease the building of Linux source code within
- * iPXE.  This is intended to facilitate quick testing; it is not
- * intended to be a substitute for proper porting.
- */
-
-FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
-
-#include <stdint.h>
-#include <errno.h>
-#include <stdio.h>
-#include <byteswap.h>
-#include <ipxe/bitops.h>
-
-#define __init
-#define __exit
-#define __initdata
-#define __exitdata
-#define printk printf
-
-#endif /* _IPXE_LINUX_COMPAT_H */