stm32mp: compute ram_top based on the optee base address only for STM32MP1

stm32mp: compute ram_top based on the optee base address only for STM32MP1

Reserved memory for OP-TEE is located at end of DDR for STM32MP1 SoC only
(STM32MP13 and STM32MP15) and the OP-TEE reserved memory is located at the
beginning of DDR for STM32MP25 SoC, before CONFIG_TEXT_BASE and
with reserved memory for companion coprocessor. So the ram_top is limited
by OP-TEE reserved memory only for STM32MP1 SoC.

This patch solves an issue for ram_top value on STM32MP25 SoC because the
generic reserved memory management, based on LMB, is no more used before
relocation.

Fixes: 8242f14a3e6f ("stm32mp: compute ram_top based on the optee base address")
Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>