hwmon: (amd_energy) Update driver documentation

Update the documentation with the newly added features
* Set the accumulation interval based on resolution

Signed-off-by: Naveen Krishna Chatradhi <nchatrad@amd.com>
Link: https://lore.kernel.org/r/20200929105322.8919-5-nchatrad@amd.com


Signed-off-by: Guenter Roeck <linux@roeck-us.net>