ARM: dts: am33xx: fix clock node definitions to avoid build warnings

Upcoming change to DT compiler is going to complain about nodes
which have a reg property, but have not defined the address in their
name. This patch fixes following type of warnings for AM33xx clock nodes:

Warning (unit_address_vs_reg): Node /ocp/cm@48004000/clocks/dpll3_m2_ck
has a reg or ranges property, but no unit name
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>