dt-bindings: interconnect: Fix the expected number of cells

dt-bindings: interconnect: Fix the expected number of cells

"make dtbs_check" complains that the number of interconnect-cells
for some RPMh platforms is not "const: 1" (as defined in the schema).

That's because the interconnect-cells now can be 1 or 2, depending
on what is supported by the specific interconnect provider. Let's
reflect this in the schema.

Fixes: 9a34e7ad2e12 ("dt-bindings: interconnect: Document the support of optional path tag")
Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>
Link: https://lore.kernel.org/r/20210121145320.2383-1-georgi.djakov@linaro.org
Signed-off-by: Rob Herring <robh@kernel.org>