ARM: davinci: da850: add dsp clock definition

Added dsp clock definition, keyed to "davinci-rproc.0".
DSP clocks is derived from pll0 sysclk1. Add a clock tree
node for that too.

Signed-off-by: Robert Tivy <rtivy@ti.com>
[nsekhar@ti.com: merge addition of pll0 sysclk1 and dsp clock
into one commit. Add PSC_FORCE to dsp clock node to handle the
case where DSP does not go into IDLE and its clock needs to
be disabled.]
Signed-off-by: Sekhar Nori <nsekhar@ti.com>