gpio: omap: Remove redundant dev_err_probe() and zero value handle code

There is no need to call the dev_err_probe() function directly to print
a custom message when handling an error from platform_get_irq() function as
it is going to display an appropriate error message in case of a failure.

And the code to handle bank->irq = 0 is redundant because
platform_get_irq() do not return 0.

Signed-off-by: Ruan Jinjie <ruanjinjie@huawei.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>