ARM: OMAP4: clock: Add CPU local timer clock node

Local timer clock is sourced from the CPU clock and hence changes
along with CPU clock. These per CPU local timers are used as
clock-events, so they need to be reconfigured on CPU frequency
change as part of CPUfreq governor.

Newly introduced clockevents_reconfigure() needs to know the
twd clock-rate. Provide a clock-node to make clk_get_rate() work
for TWD.

Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Cc: Paul Walmsley <paul@pwsan.com>
Cc: Kevin Hilman <khilman@ti.com>
[paul@pwsan.com: renamed clock node to 'mpu_periphclk' to indicate that this
 is the Cortex-A9 MPCore subsystem clock PERIPHCLK (DDI 0407G); moved
 clock and clkdev entries to match the autogenerated script output]
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>