arm64: Change kernel stack size to 16K

arm64: Change kernel stack size to 16K

commit 845ad05ec31e0f3872a321e10dbeaf872022632c upstream.

Written by Catalin Marinas, tested by APM on storm platform. This is needed
because of the failures encountered when running SpecWeb benchmark test.

Signed-off-by: Feng Kan <fkan@apm.com>
Acked-by: Kumar Sankaran <ksankaran@apm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 79f783f05539479676406d3d42c3d86bd203f083)
Signed-off-by: Mark Brown <broonie@linaro.org>