All clocks are exposed as single rate clocks.
Concerning MPU clock, only CPU OPP can act and only valid rates
are expected for this very clock.

Change-Id: I2f76135996da23dae590aa9d77e3bfd6c03a68c1
Signed-off-by: Gabriel Fernandez <gabriel.fernandez@st.com>
Reviewed-on: https://gerrit.st.com/c/mpu/oe/st/tf-a/+/185717


Reviewed-by: CITOOLS <smet-aci-reviews@lists.codex.cro.st.com>
Reviewed-by: CIBUILD <smet-aci-builds@lists.codex.cro.st.com>
Reviewed-by: Yann GAUTIER <yann.gautier@st.com>
Tested-by: Yann GAUTIER <yann.gautier@st.com>