ARM: dts: bcm: Add missing device_type = "memory" property

During the removal of the skeleton.dtsi file with commit abe60a3a
("ARM: dts: Kill off skeleton{64}.dtsi") a number of Broadcom SoCs were
converted, but a few were left unoticed, now causing boot failures with
v5.1 since the kernel cannot find suitable memory.

Updating the .dtsi files with the property will be done next, since
there are some memory nodes that do not follow the proper naming
convention and lack an unit name.

Fixes: abe60a3a ("ARM: dts: Kill off skeleton{64}.dtsi")
Reported-by: Kevin Hilman <khilman@kernel.org>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>