Documentation/amd-pstate: List amd_pstate_prefcore_ranking sysfs file

Documentation/amd-pstate: List amd_pstate_prefcore_ranking sysfs file

Add the missing amd_pstate_prefcore_ranking filenames in the sysfs
listing example leading to the descriptions of these
parameters. Clarify when will the file be visible.

Fixes: 15a2b764ea7c ("amd-pstate: Add missing documentation for `amd_pstate_prefcore_ranking`")
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Signed-off-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>