fix compile error introduced by LoongArch commit

LoongArch inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I6MV9N



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when compile kernel using the following steps:

make allmodconfig ARCH=x86_64 CROSS_COMPILE=x86_64-linux-gnu-
make oldconfig ARCH=x86_64 CROSS_COMPILE=x86_64-linux-gnu-
make -j64 ARCH=x86_64 CROSS_COMPILE=x86_64-linux-gnu-

we get error:

  DESCEND  objtool
  HOSTCC  scripts/sorttable
In file included from scripts/sorttable.c:195:
scripts/sorttable.h:89:10: fatal error: asm/orc_types.h: No such file or directory
   89 | #include <asm/orc_types.h>
      |          ^~~~~~~~~~~~~~~~~
compilation terminated.
make[1]: *** [scripts/Makefile.host:95: scripts/sorttable] Error 1
make: *** [Makefile:1215: scripts] Error 2
make: *** Waiting for unfinished jobs....

the reason is ARCH a command-line variable,the normal assignment is
ignored.So split loongarch architecture from others.

Fixes: 4efd0de6 ("tools/perf: Add basic support for LoongArch")
Signed-off-by: Hongchen Zhang <zhanghongchen@loongson.cn>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
Signed-off-by: Jialin Zhang <zhangjialin11@huawei.com>