Simple patch to make symbols static. Symbols that are not
shared with other parts of the kernel can be made static.
This change also removes several sparse complains.

Cc: Zhang Rui <rui.zhang@intel.com>
Cc: Lee Jones <lee.jones@linaro.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Ajit Pal Singh <ajitpal.singh@st.com>
Cc: linux-pm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: NEduardo Valentin <edubezval@gmail.com>