arm64: dts: meson-g12: drop BL32 region from SEI510/SEI610

The BL32/TEE reserved-memory region is now inherited from the common
family dtsi (meson-g12-common) so we can drop it from board files.

Signed-off-by: Christian Hewitt <christianshewitt@gmail.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://lore.kernel.org/r/20220126044954.19069-4-christianshewitt@gmail.com