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

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

This reverts commit 3214ba151955283013f78eeaabd3b0d64d499212.

This is no longer needed since the following commit and to the best
of my knowledge is not relied on by any upstream DTS:

e0b486e07a8f (cpufreq: dt-platdev: Automatically create cpufreq
device with OPP v2)

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>