davinci: make /proc/davinci_clocks display multi-rooted clock tree

This patch modifies clock dump to take care of
clock tress rooted at multiple oscillators.
Current code assumes the entire tree is rooted
on a single oscillator. When using off-chip
clock synthesizers, some of the clocks can
be obtained from a different on-board oscillator.

Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>