dt-bindings: soc: ti: pruss: Add documentation for PA_STATS support

dt-bindings: soc: ti: pruss: Add documentation for PA_STATS support

Add documentation for pa-stats node which is syscon regmap for
PA_STATS registers. This will be used to dump statistics maintained by
ICSSG firmware.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Roger Quadros <rogerq@kernel.org>
Acked-by: Nishanth Menon <nm@ti.com>
Signed-off-by: MD Danish Anwar <danishanwar@ti.com>
Link: https://patch.msgid.link/20240822122652.1071801-2-danishanwar@ti.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>