microblaze: Convert headers to SPDX license

Covert all headers to SPDX.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Stefan Asserhall <stefan.asserhall@xilinx.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>

Disintegrate asm/system.h for Microblaze

Disintegrate asm/system.h for Microblaze. Not compiled.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: microblaze-uclinux@itee.uq.edu.au