plat/st: move GPIO bank helper function to platform source files

Relation between GPIO banks and their base address and offset address
if platform dependent. This change moves helper functions
stm32_get_gpio_bank_base() and stm32_get_gpio_bank_offset() from
plat/st/common to plat/st/stm32mp1/.

Change-Id: Id3d03e585746aa5509c6fab7d88183a92d561e3f
Signed-off-by: Etienne Carriere <etienne.carriere@st.com>
2 files changed