Fix missed serial input signal changes caused by rereading the serial
status register during interrupt processing.  Now processing is performed
on original status register value.
Signed-off-by: Paul Fulghum <paulkf@microgate.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>