serial: pic32_uart: Convert to use GPIO descriptors

Plain global GPIO numbering schema is deprecated and is being removed
from the kernel. Convert this driver to use a new GPIO descriptor based
schema.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220806225643.40897-2-andriy.shevchenko@linux.intel.com


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