Replaces the deprecated __attribute_used__ with __used.  Also makes some
style adjustments to abide by the kernel coding conventions.

Cc: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>