Revert "dt-bindings: remoteproc: pru: Document application node bindings"

This reverts commit 286069bc.

The plain text-format binding document update to the PRU remoteproc
binding for the PRU application nodes has been replaced by a separate
equivalent upstream preferred YAML-format binding document in
commit 8f54d76f ("dt-bindings: remoteproc: Add PRU consumer
bindings"), so revert the above text-based binding update patch.

Signed-off-by: Suman Anna <s-anna@ti.com>