board: stm32mp1: update fdt fixup partitions table

This patch adds "st,stm32mp1-fmc2-nfc" compatible string in the
fdt fixup partitions table.

Signed-off-by: Christophe Kerello <christophe.kerello@st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@st.com>