scmi_clock: clean up policy functions

This patch cleans up the policy functions from the `scmi_clock` module.
As seen in `c49f0437`, due to the code complexity of the function can
potentially introduce defects that can be difficult to spot and maintain.
Refactoring `mod_scmi_clock_config_set_policy` function also helps to
reduce the number of function calls and processing time, which can
improve performance and efficiency.

Furthermore, this commit refactors the module by removing all unnecessary
parameters in helper functions.

In addition, removing the FWK_WEAK to enforce the current policy until
further requirements.

Signed-off-by: Leandro Belli <leandro.belli@arm.com>
Signed-off-by: Mohamed Omar Asaker <mohamed.omarasaker@arm.com>
Change-Id: I03edb2306d6e7acd1cd77168a6d5144fa2c291fa