dt-bindings: fsi: Document the FSI controller common properties

dt-bindings: fsi: Document the FSI controller common properties

Since there are multiple FSI controllers documented, the common
properties should be documented separately and then referenced
from the specific controller documentation. Add bus-frequency for
the FSI bus and CFAM local bus frequencies. Add interrupt
controller properties.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20240522192524.3286237-7-eajames@linux.ibm.com
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>