bpf, arm64: Remove redundant switch case about BPF_DIV and BPF_MOD

After commit 96a71005 ("bpf, arm64: remove obsolete exception handling
from div/mod"), there is no need to check twice about BPF_DIV and BPF_MOD,
remove the redundant switch case.

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/1621328170-17583-1-git-send-email-yangtiezhu@loongson.cn