ARM: OMAP: serial: Fix the ocp smart idlemode handling bug

The current serial UART code, while fidling with ocp idlemode bits,
forget about the smart idle wakeup bit even if it is supported by
UART IP block. This will lead to missing the module wakeup on OMAP's
where the smart idle wakeup is supported.

This was the root cause of the console sluggishness issue, I have been
observing on OMAP4 devices and also can be potential reason for some
other UART wakeup issues.

Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Kevin Hilman <khilman@ti.com>
Acked-by: Govindraj.R <govindraj.raja@ti.com>
Reviewed-by: Paul Walmsley <paul@pwsan.com>
Cc: stable@vger.kernel.org
Signed-off-by: Tony Lindgren <tony@atomide.com>