bus: ti-sysc: Remove open coded "ranges" parsing

"ranges" is a standard property and we have common helper functions for
parsing it, so let's use them.

Signed-off-by: Rob Herring <robh@kernel.org>
Message-Id: <20230201220002.246907-1-robh@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>