tty/serial: Prevent drop of DCD on suspend for Tegra UARTs"

This reverts commit 9636b755da7b498094bdf15b4ce9f6fd16995e4e.

It wasn't supposed to be applied, thanks to Doug for letting me know.

Cc: Doug Anderson <dianders@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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