bus: rifsc: add debugfs entry to dump the firewall configuration

RIFSC configuration can be difficult to debug. Add a debugfs entry
that dumps the configuration of the RISUPs, the RISALs and the RIMUs.
This will allow to display the whole RIFSC firewall configuration at
runtime.

While there, fix a bug on the computation of firewall entries in the
probe function.

Signed-off-by: Gatien Chevallier <gatien.chevallier@foss.st.com>
Link: https://lore.kernel.org/r/20251106-rifsc_debugfs-v2-3-f90e94ae756d@foss.st.com
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>

Author: GseoC