stm32mp1: use clock rate description by step for all clocks

Remove rate description by arrays as Linux kernel does not properly
handle rate arrays.

Change-Id: I1ee37b8f5e3f10a03dee9f2ed3c699777840e3e9
Signed-off-by: Gabriel Fernandez <gabriel.fernandez@st.com>
Reviewed-on: https://gerrit.st.com/c/mpu/oe/st/tf-a/+/185718


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>