linux-phytec-ti

remoteproc/pru: add APIs to get and put the PRU cores

Add two new APIs, pru_rproc_get() and pru_rproc_put(), to the PRU
driver to allow client drivers to acquire and release the remoteproc
device associated with a PRU core. The PRU cores are treated as
resources with only one client owning it at a time.

The pru_rproc_get() function returns the rproc handle corresponding
to a PRU core identified by the device tree "prus" property under
the client node. The pru_rproc_put() is the complementary function
to pru_rproc_get().

Signed-off-by: Tero Kristo <t-kristo@ti.com>
[s-anna@ti.com: improve error checking, various fixes and cleanups]
Signed-off-by: Suman Anna <s-anna@ti.com>