Add a missing #define for the platform_kernel_launch_event.  Without this
fix, a call to platform_kernel_launch_event() becomes a noop on generic
kernels.  SN systems require this fix to successfully kdump/kexec from
certain hardware errors.

[bwalle@suse.de: fix it]
Signed-off-by: John Keller <jpk@sgi.com>
Cc: Bernhard Walle <bwalle@suse.de>
Acked-by: Simon Horman <horms@verge.net.au>
Acked-by: Jay Lan <jlan@sgi.com>
Acked-by: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>