quickstart: update DUT kernel and GCC version

Updated the validated kernel and gcc version in quickstart guide.

Signed-off-by: Lijian Zhang <Lijian.Zhang@arm.com>
Reviewed-by: Tianyu Li <tianyu.li@arm.com>
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>

Change-Id: I18020997196df12be67a20e62f9c4ceffdfd460b