fix a braino in compat_sys_getrlimit()

Reported-and-tested-by: Meelis Roos <mroos@linux.ee>
Fixes: commit d9e968cb "getrlimit()/setrlimit(): move compat to native"
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>