LoongArch: Flush TLB earlier at initialization

LoongArch inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I736HO



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Move local_flush_tlb_all() earlier (just after setup_ptwalker() and
before page allocation). This can avoid stale TLB entries misguiding
the later page allocation. Without this patch the second kernel of
kexec/kdump fails to boot SMP.

Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Youling Tang <tangyouling@loongson.cn>
Change-Id: I118e0c8aafabfef28bc47a0d06286db850b6e79e