ti_config_fragments: v8_rpmsg: Enable PRUSS support

The PRUSS platform/remoteproc drivers also support the newer
PRUSS IPs called ICSSG on the K3 family of SoCs. Add support
to build these PRUSS platform/remoteproc drivers. The PRU RPMsg
driver is also explicitly enabled as these are needed to showcase
the remoteproc/rpmsg communication with the PRU/RTU cores within
the ICSSG instances. All of these drivers will be built as modules
by default.

Signed-off-by: Suman Anna <s-anna@ti.com>