ARM: dts: keystone-k2l-clocks: Add missing unit name to clock nodes that have regs

Add the control register as the base for the clock nodes which are
missing them. This squashes some 22 warnings of the effect when built
with W=1.

Reported-by: Rob Herring <robh@kernel.org>
Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>