driver core: platform: Declare ret variable only once

We may define ret variable only once and avoid adding it each time
platform_get_irq_optional() get extended.

For the sake of consistency do the same in __platform_get_irq_byname().

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20191023122505.64684-1-andriy.shevchenko@linux.intel.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>