scmi_clock: Return the SCMI agent's state instead of the physical state

The current method of reading the clock state calls the Clock HAL directly,
which can cause inconsistencies between what is being read by Clock Hal and
what is being set in the SCMI agent state table.
To address this, the existing `scmi_clock_get_agent_clock_state`
helper function is used to read the clock state in relation to the
requesting SCMI agent.
i.e. function returns the state expected by SCMI agent.

Signed-off-by: Leandro Belli <leandro.belli@arm.com>
Signed-off-by: Mohamed Omar Asaker <mohamed.omarasaker@arm.com>
Change-Id: I8f0f00dc06eecd21803983837f3a7f27d0033723