mm: don't warn when vmalloc() fails due to a fatal signal

When vmalloc() fails it prints a very lengthy message with all the
details about memory consumption assuming that it happened due to OOM.

However, vmalloc() can also fail due to fatal signal pending.  In such
case the message is quite confusing because it suggests that it is OOM
but the numbers suggest otherwise.  The messages can also pollute
console considerably.

Don't warn when vmalloc() fails due to fatal signal pending.

Link: http://lkml.kernel.org/r/20170313114425.72724-1-dvyukov@google.com
Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Matthew Wilcox <mawilcox@microsoft.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>