Add a sysrq-trigger mechanism for kexec based crashdumps.  Alt-Sysrq-c
triggers a kexec based crashdump.
Signed-off-by: NHariprasad Nellitheertha <hari@in.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>