soc: ti: pruss: Add support for PRU-ICSS0 on AM437x SoCs

soc: ti: pruss: Add support for PRU-ICSS0 on AM437x SoCs

The AM437x SoCs have a second smaller PRU-ICSS subsystem (PRUSS0)
in addition to the primary PRUSS1 instance. The PRUSS0 is another
instantiation of the IP, but is not identical to PRUSS1. It is
essentially a cut-down version of the IP, with less DRAM per PRU,
no Shared DRAM etc. It also does not have direct access to L3 bus
regions, there is a single interface to L3 for both PRUSS0 and
PRUSS1, and it would have to go through the PRUSS1's interface.
The PRUSS_SYSCFG register is reserved on PRUSS0, so any external
access requires the programming the corresponding PRUSS_SYSCFG
register in PRUSS1. It does have its own dedicated I/O lines
though. Note that this instance does not support any PRU Ethernet
related usecases.

The PRUSS remoteproc drivers have been enhanced to support this
smaller PRUSS0 instance using instance-specific data. The adaptation
uses a newly introduced pruss_match_private_data structure and the
pruss_get_private_data() function to retrieve a PRUSS instance
specific data using a device-name based lookup logic. The reset
and the L3 external access are managed by the common PRUSS SoC bus
driver so that PRUSS1 and PRUSS0 can be independently supported.
The initial names for the firmware images for each PRU core are
retrieved from DT nodes, and can be adjusted through sysfs if
required.

Signed-off-by: Andrew F. Davis <afd@ti.com>
Signed-off-by: Suman Anna <s-anna@ti.com>