csky: syscache: Fixup duplicate cache flush

stable inclusion
from stable-5.10.50
commit b6a41435c832830754ed298e9ae2eaf13e74e88f
bugzilla: 174522 https://gitee.com/openeuler/kernel/issues/I4DNFY

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b6a41435c832830754ed298e9ae2eaf13e74e88f



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[ Upstream commit 6ea42c84 ]

The current csky logic of sys_cacheflush is wrong, it'll cause
icache flush call dcache flush again. Now fixup it with a
conditional "break & fallthrough".

Fixes: 997153b9 ("csky: Add flush_icache_mm to defer flush icache all")
Fixes: 0679d29d ("csky: fix syscache.c fallthrough warning")
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Co-Developed-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Acked-by: Weilong Chen <chenweilong@huawei.com>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>