System clock for m4 core was set to same clock as m7 core.
This is wrong as m4 its value is actually based on clock frequency
value after D1CPRE (sys_d1cpre_ck) divided per HPRE value, 200MHz in
current case.
This also matches the max clock speed for the m4 core (200MHz)
Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>