pinctrl: intel: refine ->irq_set_type() hook

Refine ->irq_set_type() hook and improve its readability by:

- Reducing scope of spinlock by moving unneeded operations out of it.
- Dropping redundant PADCFG0_RXEVCFG_SHIFT and including it directly
  into PADCFG0_RXEVCFG_* definitions.
- Utilizing temporary variables for common operations.
- Simplifying if-else-if chain.

Signed-off-by: Raag Jadav <raag.jadav@intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>