MIPS: dts: loongson: Fix ls2k1000-rtc interrupt

[ Upstream commit f70fd92df7529e7283e02a6c3a2510075f13ba30 ]

The correct interrupt line for RTC is line 8 on liointc1.

Fixes: e47084e1 ("MIPS: Loongson64: DTS: Add RTC support to Loongson-2K1000")
Cc: stable@vger.kernel.org
Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>