ARM: dts: ls1021a: add nodes for on-chip ram

Although the two nodes constitute one contiguous 128K region, still
describe them separately:

- That's how they are described in the reference manual: "Each OCRAM
  occupies a 64 KB of address region...", and the names ocram1 and
  ocram2 are also as used in the manual.

- The two areas are treated differently by the boot ROM code: OCRAM2 is
  zero-initialized, while, again quoting the RM, "software must perform
  the zero initialization of OCRAM1."

Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>