uboot-imx

arm: timer: get frequency for arch timer armv7 in cp15 cntfrq

Manage dynamic value for armv7 arch clock timer,
when CONFIG_SYS_HZ_CLOCK is not defined.
Get frequency from CP15 cntfrq information, initialized for example
by first boot stage, clock driver or by BootRom.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>