Documentation: intel-pstate: Use :ref: directive for internal linking

Documentation: intel-pstate: Use :ref: directive for internal linking

intel_pstate docs uses standard reST construct (`Section title`_) for
cross-referencing sections (internal linking), rather than for external
links. Incorrect cross-references are not caught when these are written
in that syntax, however (fortunately docutils 0.22 raise duplicate
target warnings that get fixed in cb908f8b0acc7e ("Documentation:
intel_pstate: fix duplicate hyperlink target errors")).

Convert the cross-references to use :ref: directive, which doesn't
exhibit this problem.

Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
[ rjw: Changelog tweak ]
Link: https://patch.msgid.link/20251101055614.32270-1-bagasdotme@gmail.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>