microblaze: Cleanup linker script using new linker script macros.

I wasn't able to further clean up the linker script using the
INIT_DATA_SECTION macro because of the FIXME comment for the
.init.ramfs section; when that is resolved we should convert
microblaze to use INIT_DATA_SECTION.

Signed-off-by: Tim Abbott <tabbott@ksplice.com>
Cc: Michal Simek <monstr@monstr.eu>
Cc: microblaze-uclinux@itee.uq.edu.au
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Michal Simek <monstr@monstr.eu>