Introduce is_sysrq_oom helper function indicating oom kill triggered
by sysrq to improve readability.

No functional changes.
Signed-off-by: NYaowei Bai <bywxiaobai@163.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Acked-by: NMichal Hocko <mhocko@suse.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>