LoongArch: remove __ARCH_WANT_NEW_STAT

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



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remove fstatat and fstat syscall, not used by glibc now.

Signed-off-by: Hongchen Zhang <zhanghongchen@loongson.cn>
Change-Id: Ib54607ad15bdb7fa59626caebd851312c490d897