ARM: stm32: Set environment sector size to 4k on DHSOM

The DHSOM SPI NOR is using 4k erase blocks, make use of it
and define the default environment sector size to 4k.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Patrice Chotard <patrice.chotard@foss.st.com>
Cc: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>
2 files changed