gpio/omap: fix possible memory leak in omap2_gpio_dev_init()

pdata and pdata->regs have been allocated in this function and
should be freed before leaving it, and in the other error handling
cases too.

spatch with a semantic match is used to found this problem.
(http://coccinelle.lip6.fr/)

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Acked-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>