defconfig: sdm845: Enable stack protector strong

Change build from using configuration option stack protector regular
to stack protector strong. With stack protector strong more functions
will be protected from stack overflow.

Change-Id: I7358570557f7543a5b6ebc51736ccc2f860e260a
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>