dt/bindings: fwu-mdata-mtd: drop changes outside FWU

dt/bindings: fwu-mdata-mtd: drop changes outside FWU

Any requirement of FWU should not require changes to bindings
of other subsystems. For example, for mtd-backed storage we
can do without requiring 'fixed-partitions' children to also
carry 'uuid', a property which is non-standard and not in the
bindings.

 There exists no code yet, so we can change the fwu-mtd bindings
to contain all properties within the fwu-mdata node.

Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Tested-by: Sughosh Ganu <sughosh.ganu@linaro.org>