I2C: OMAP: Do not set the XUDF(Transmit underflow) if the underflow is not reached

Currently in the 1.153 errata handling, while waiting for transmitter
underflow, if NACK is got the XUDF(Transmit underflow) flag is also set.
Fix this by setting the XUDF(Transmit underflow) flag after wait for the
condition is over.

Cc: Alexander Shishkin <virtuoso@slind.org>
Acked-by: Moiz Sonasath <m-sonasath@ti.com>
Reviewed-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Shubhrajyoti D <shubhrajyoti@ti.com>
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>