stm32mp1: update device tree and gpio functions

Change fdt_check_status function to fdt_get_status.
Update GPIO defines.
Move some functions in gpio driver, instead of dt helper file.
Add GPIO bank helper functions.
Use only one status field in dt_node_info structure including both status
and secure status.

Change-Id: I34f93408dd4aac16ae722f564bc3f7d6ae978cf4
Signed-off-by: Yann Gautier <yann.gautier@st.com>
Signed-off-by: Etienne Carriere <etienne.carriere@st.com>
Signed-off-by: Lionel Debieve <lionel.debieve@st.com>
Signed-off-by: Nicolas Le Bayon <nicolas.le.bayon@st.com>