MIPS: loongson32: ls1c: Fix hang during startup

[ Upstream commit 35508d2424097f9b6a1a17aac94f702767035616 ]

The RTCCTRL reg of LS1C is obselete.
Writing this reg will cause system hang.

Fixes: 60219c56 ("MIPS: Add RTC support for Loongson1C board")
Signed-off-by: Yang Ling <gnaygnil@gmail.com>
Tested-by: Keguang Zhang <keguang.zhang@gmail.com>
Acked-by: Keguang Zhang <keguang.zhang@gmail.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>