[submodule]: update sonic-linux-kernel

* 6aa8d00 2021-11-12 | marvell-armhf]: add kconfig force inclusion for CONFIG_ARCH_NR_GPIO (sonic-net#245) (HEAD, origin/master, origin/HEAD) [dflynn-Nokia]
* 39c7d18 2021-11-06 | [arm64]: add kconfig force inclusion for COMPAT_VSDO [Guohan Lu]
* fafaaea 2021-11-06 | [backport] kernel-compat-always-include-linux-compat.h-from-net-compat.patch [Guohan Lu]
* 6ac9b48 2021-10-19 | [ci]: use native arm64/armhf pool to build kernel [Guohan Lu]

Signed-off-by: Guohan Lu <[email protected]>