nios2: fix flush_dcache_page() for usage from irq context

nios2: fix flush_dcache_page() for usage from irq context

Since at least kernel 6.1, flush_dcache_page() is called with IRQs
disabled, e.g.  from aio_complete().

But the current implementation for flush_dcache_page() on NIOS2
unintentionally re-enables IRQs, which may lead to deadlocks.

Fix it by using xa_lock_irqsave() and xa_unlock_irqrestore() for the
flush_dcache_mmap_*lock() macros instead.

Link: https://lkml.kernel.org/r/ZOTF5WWURQNH9+iw@p100
Signed-off-by: Helge Deller <deller@gmx.de>
Cc: Dinh Nguyen <dinguyen@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>