Introduce helper functions stm32mp_register_secure_periph_iomem()
and stm32mp_register_non_secure_periph_iomem() for drivers to
register a resource as secure or non-secure based on its SoC
interface registers base address.

These functions are stubbed when shared resources driver is not
embedded (!STM32MP_SHARED_RESOURCES) so that drivers embedded
in other BL stages do not bother whether they shall register or
not their resources.

Change-Id: Icebd05a930afc5964bc4677357da5d1b23666066
Signed-off-by: Etienne Carriere <etienne.carriere@st.com>