frv: build fix

In file included from /usr/src/linux-2.6-2/net/ipv4/ip_input.c:118:

  include2/asm/system.h:245: error: parse error before "__cmpxchg_32"
  include2/asm/system.h:245: error: parse error before '*' token
  include2/asm/system.h:245: warning: type defaults to `int' in declaration of `__cmpxchg_32'
  include2/asm/system.h:245: warning: function declaration isn't a prototype
  include2/asm/system.h:245: warning: data definition has no type or storage class

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>