power: clarify comment about SST-BF priority core

As part of the documentation update on the changes made to the power
library for 19.05, information on SST-BF was added. This patch updates
the comment to clarify that a priority core is an SST-BF high
frequency core.

Signed-off-by: David Hunt <david.hunt@intel.com>
Acked-by: John McNamara <john.mcnamara@intel.com>

lib/librte_power/rte_power.h

@@ -259,7 +259,7 @@ struct rte_power_core_capabilities {
 		RTE_STD_C11
 		struct {
 			uint64_t turbo:1;	/**< Turbo can be enabled. */
-			uint64_t priority:1;	/**< Priority core */
+			uint64_t priority:1;	/**< SST-BF high freq core */
 		};
 	};
 };