serial: pic32: free up irq names correctly

struct pic32_sport contains built-up names for irqs. These are freed
only in error path of pic32_uart_startup(). And even there, the freeing
happens before free_irq().

So fix this by:
* moving frees after free_irq(), and
* add frees to pic32_uart_shutdown() -- the opposite of
  pic32_uart_startup().

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220503063122.20957-11-jslaby@suse.cz


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