linux-yocto: x86_64: expand kernel stack to 16K

linux-yocto: x86_64: expand kernel stack to 16K

Updating to backport the following mainline commit:

[
    x86_64: expand kernel stack to 16K

    commit 6538b8ea886e472f4431db8ca1d60478f838d14b upstream

    While I play inhouse patches with much memory pressure on qemu-kvm,
    3.14 kernel was randomly crashed. The reason was kernel stack overflow.

    When I investigated the problem, the callstack was a little bit deeper
    by involve with reclaim functions but not direct reclaim path.

   ....
]

(From OE-Core rev: b162bcf26a5b97fddd2a64789f97ec705bb354f9)

Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>