cpufreq: dt: Add r8a7796 support to to use generic cpufreq driver

cpufreq: dt: Add r8a7796 support to to use generic cpufreq driver

This patch adds the r8a7796 support the generic cpufreq driver
by adding an appropriate compat string. This is in keeping
with support for other Renesas ARM and arm64 based SoCs.

Signed-off-by: Khiem Nguyen <khiem.nguyen.xt@rvc.renesas.com>
[simon: new changelog]
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>