The interrupt service routine is always invoked with disabled
interrupts.

Remove the _irqsave() from the locking functions in the interrupts
service routine/ pch_uart_interrupt().
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20240301215246.891055-16-bigeasy@linutronix.deSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>