GitLab

Get number of pins in the GPIOZ bank with helper function
fdt_get_gpio_bank_pin_count(). Save the value in RAM to prevent
parsing the FDT several time for the same information.

Change-Id: Ie68e300804461ffce09914100a7d2962116023b5
Signed-off-by: Etienne Carriere <etienne.carriere@st.com>