ARM: stm32: fix stm32f7 sdram fmc base address

The fmc base address is defined twice, once in fmc.h and once in stm32.h.
Fix wrong definition in stm32.h.
Remove the definiton in fmc.h.

Signed-off-by: Michael Kurz <michi.kurz@gmail.com>
Acked-by: Vikas Manocha <vikas.manocha@st.com>