[SPARC]: avoid CHILD_MAX and OPEN_MAX constants

I don't figure anyone really cares about SunOS syscall emulation, and I
certainly don't.  But I'm getting rid of uses of the OPEN_MAX and CHILD_MAX
compile-time constant, and these are almost the only ones.  OPEN_MAX is a
bogus constant with no meaning about anything.  The RLIMIT_NOFILE resource
limit is what sysconf (_SC_OPEN_MAX) actually wants to return.

The CHILD_MAX cases weren't actually using anything I want to get rid of,
but I noticed that they are there and are wrong too.  The CHILD_MAX value
is not really unlimited as a -1 return from sysconf indicates.  The
RLIMIT_NPROC resource limit is what sysconf (_SC_CHILD_MAX) wants to return.

Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>