board: st: stm32mp1: increase teed partition

With TEE 3.7.0, the partition teed (OP-TEE pageable
code and data) need to increase up to 512KB in NOR device.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@st.com>