LoongArch: Add vector extensions support

LoongArch inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I6BWFP



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Add LoongArch's vector extensions support, which including 128bit LSX
(i.e., Loongson SIMD eXtension) and 256bit LASX (i.e., Loongson Advanced
SIMD eXtension).

Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Change-Id: Icbdcc8c0657d85198accb9050f90dd41c9fa456c
(cherry picked from commit 18c5e807)