refactor(st-pmic): improve driver usage

Store status of dt_pmic_status() as local static variable,
this avoids parsing DT several times.
In the same way, store nodes in dt_pmic_i2c_config() and
in dt_get_pmic_node() as local static variables.

Change-Id: I4585e9dfdde2847a369bffcc6f2b39ecc2b74de1
Signed-off-by: Nicolas Le Bayon <nicolas.le.bayon@st.com>
1 file changed