compat_ioctl: Avoid using undefined RS-485 IOCTLs

Wrap the use of TIOCSRS485 and TIOCGRS485 in #ifdef so that we avoid
adding undefined IOCTLs to the ioctl pointer list as compatible
ioctls.

This change was motivated by a build error on a MIPS build.

tree:   git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git


tty-next
head:   ac57e7f3
commit: 84c3b848 [10/16] compat_ioctl:
  Add RS-485 IOCTLs to the list
config: mips-fuloong2e_defconfig

All related error/warning messages:

fs/compat_ioctl.c:869:1: error: 'TIOCSRS485' undeclared here (not in a
  function)
fs/compat_ioctl.c:870:1: error: 'TIOCGRS485' undeclared here (not in a
  function)

vim +869 fs/compat_ioctl.c
863 COMPATIBLE_IOCTL(TIOCSPGRP)
864 COMPATIBLE_IOCTL(TIOCGPGRP)
865 COMPATIBLE_IOCTL(TIOCGPTN)
866 COMPATIBLE_IOCTL(TIOCSPTLCK)
867 COMPATIBLE_IOCTL(TIOCSERGETLSR)
868 COMPATIBLE_IOCTL(TIOCSIG)
> 869 COMPATIBLE_IOCTL(TIOCSRS485)
870 COMPATIBLE_IOCTL(TIOCGRS485)
871 #ifdef TCGETS2
872 COMPATIBLE_IOCTL(TCGETS2)

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Jaeden Amero <jaeden.amero@ni.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>