remoteproc: pru: Add enum for PRU Core Identifiers.

Introducing enum pruss_pru_id for PRU Core Identifiers.
PRUSS_PRU0 indicates PRU Core 0.
PRUSS_PRU1 indicates PRU Core 1.
PRUSS_NUM_PRUS indicates the total number of PRU Cores.

Signed-off-by: MD Danish Anwar <danishanwar@ti.com>
Reviewed-by: Roger Quadros <rogerq@kernel.org>
Link: https://lore.kernel.org/r/20230106121046.886863-3-danishanwar@ti.com


Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>