soc: ti: pruss: Add helper functions to set GPI mode, MII_RT_event and XFR

soc: ti: pruss: Add helper functions to set GPI mode, MII_RT_event and XFR

The PRUSS CFG module is represented as a syscon node and is currently
managed by the PRUSS platform driver. Add easy accessor functions to set
GPI mode, MII_RT event enable/disable and XFR (XIN XOUT) enable/disable
to enable the PRUSS Ethernet usecase. These functions reuse the generic
pruss_cfg_update() API function.

Signed-off-by: Suman Anna <s-anna@ti.com>
Co-developed-by: Grzegorz Jaszczyk <grzegorz.jaszczyk@linaro.org>
Signed-off-by: Grzegorz Jaszczyk <grzegorz.jaszczyk@linaro.org>
Signed-off-by: Puranjay Mohan <p-mohan@ti.com>
Reviewed-by: Roger Quadros <rogerq@kernel.org>
Reviewed-by: Tony Lindgren <tony@atomide.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: MD Danish Anwar <danishanwar@ti.com>
Link: https://lore.kernel.org/r/20230414045542.3249939-5-danishanwar@ti.com
Signed-off-by: Nishanth Menon <nm@ti.com>