dt-bindings: sram: Allow for the childs nodes to be called sections

The generic SRAM binding currently only allows for child nodes of an SRAM
to be called sram too. However, these are also called sections in a number
of device tree, which seems a bit more accurate.

Let's change the name pattern to allow both.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Signed-off-by: Rob Herring <robh@kernel.org>