checkpatch: add rules to check init attribute and const defects

People get this regularly wrong and it breaks the LTO builds, as it causes
a section attribute conflict.

Add --fix capability too.

Based on a patch from Andi Kleen.

Signed-off-by: Joe Perches <joe@perches.com>
Cc: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>