Check for changed gaurd macro in 2.6.28+ for rwsem implementation.

Check for changed gaurd macro in 2.6.28+ for rwsem implementation.

As part of the 2.6.28 cleanup which moved all the linux/include/asm/
headers in to linux/arch, the guard headers for many header files
changed.  The i386 rwsem implementation keys off this header to
ensure the internal members of the rwsem structure are interpreted
correctly.  This change checks for the new guard macro in addition
to the only one, the implementation of the rwsem has not changed
for i386 so this is safe and correct.