SPORT transmit frame sync (TFS) isn't used as an electrical signal during
normal SPORT UART emulation.  However, it is useful in EIA RS-485
emulation as RS-485 Transceiver Driver Enable DE strobe.

This patch configures:
TFS to be active high in order to drive an DE strobe of
an eventually connected RS-485 Transceiver.

Late frame sync mode (LATFS) gating the entire TX shift cycle.
Signed-off-by: NMichael Hennerich <michael.hennerich@analog.com>
Signed-off-by: NMike Frysinger <vapier@gentoo.org>
Signed-off-by: NBryan Wu <cooloney@kernel.org>
Signed-off-by: NAlan Cox <alan@linux.intel.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>