asm-generic/siginfo.h: update NSIGTRAP definition

Impact: (nearly) trivial

The patch

commit da654b74bda14c45a7d98c731bf3c1a43b6b74e2
Author: Srinivasa Ds <srinivasa@in.ibm.com>
Date:   Tue Sep 23 15:23:52 2008 +0530

    signals: demultiplexing SIGTRAP signal

forgot to update the NSIGTRAP define in asm-generic/siginfo.h to the new
number of sigtrap subcodes.  Nothing in the tree seems to use it, but
presumably something in user space might.  So update it.

Cc: Srinivasa Ds <srinivasa@in.ibm.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>