serial: pic32: restore disabled irqs in pic32_uart_startup()

serial: pic32: restore disabled irqs in pic32_uart_startup()

pic32_uart_startup() disables interrupts by local_irq_save(). But the
function never enables them. The serial core only holds a mutex, so irqs
are not restored.

So how could this driver work? This irq handling was already present in
the driver's initial commit 157b9394709ed (serial: pic32_uart: Add PIC32
UART driver).

So is it a candidate for removal? Anyone has a contact to the author:
Andrei Pistirica (I believe the one below -- @microchip.com -- will
bounce)? Or to someone else @microchip.com?

Cc: Andrei Pistirica <andrei.pistirica@microchip.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220503063122.20957-12-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>