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When system resume, we want to print log as soon as possible.
So we add uart save and restore api, and they will be called
when systtem suspend and resume.

Change-Id: I83b477fd2b39567c9c6b70534ef186993f7053ae
Signed-off-by: Yuchen Huang <yuchen.huang@mediatek.com>
Signed-off-by: Roger Lu <roger.lu@mediatek.com>