OMAP3: GPIO: Enable debounce clock only when debounce is enabled v3.

This patch changes gpio "driver" to enable debounce clock for
gpio-bank only when debounce is enabled for some gpio in that bank.

Gpio functional clocks are also renamed in clock tree, gpioX_fck ->
gpioX_dbck.

This patch triggers problem with gpio wake-up and Omap3. Gpios in PER
domain aren't capable to generate wake-up if PER domain is in sleep
state. For this iopad wake-up should be used and needed pad
configuration should be done. Enabling iopad wake-up for gpio pads is
left for bootloader or omap mux configuration in kernel.

Signed-off-by: Jouni Hogander <jouni.hogander@nokia.com>
Acked-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>