dt-bindings: memory: lpddr2: Document Elpida B8132B2PB-6D-F

Elpida B8132B2PB-6D-F memory chip is used by ASUS Transformer TF101
tablet, add compatible for it. We need to specify this compatible it
for a device-tree node containing corresponding memory timings in order
to allow software to match the timings with the detected hardware.

Signed-off-by: Dmitry Osipenko <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Krzysztof Kozlowski <[e-mail]>

Documentation/devicetree/bindings/memory-controllers/ddr/jedec,lpddr2.yaml

···
       - items:
           - enum:
               - elpida,ECB240ABACN
+              - elpida,B8132B2PB-6D-F
           - enum:
               - jedec,lpddr2-s4
       - items: