powercap: intel_rapl: Cleanup Power Limits support

The same set of operations are shared by different Powert Limits,
including Power Limit get/set, Power Limit enable/disable, clamping
enable/disable, time window get/set, and max power get/set, etc.

But the same operation for different Power Limit has different
primitives because they use different registers/register bits.

A lot of dirty/duplicate code was introduced to handle this difference.

Introduce a universal way to issue Power Limit operations.
Instead of using hardcoded primitive name directly, use Power Limit id
+ operation type, and hide all the Power Limit difference details in a
central place, get_pl_prim(). Two helpers, rapl_read_pl_data() and
rapl_write_pl_data(), are introduced at the same time to simplify the
code for issuing Power Limit operations.
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Tested-by: Wang Wendy <wendy.wang@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

include/linux/intel_rapl.h

@@ -79,7 +79,6 @@ struct rapl_domain_data {
 
 struct rapl_power_limit {
 	struct powercap_zone_constraint *constraint;
-	int prim_id;		/* primitive ID used to enable */
 	struct rapl_domain *domain;
 	const char *name;
 	u64 last_power_limit;