cpufreq: dt: Rename 'need_update' to 'opp_v1'

That's the real purpose of this field, i.e. to take special care of old
OPP V1 bindings. Lets name it accordingly, so that it can be used
elsewhere.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
(cherry picked from commit 457e99e60a8f5a40b7da204c0bfc8a86ad2161b9)
Signed-off-by: Alex Shi <alex.shi@linaro.org>