Documentation: tps6594-pfsm: Fix macro cross-reference syntax

Documentation: tps6594-pfsm: Fix macro cross-reference syntax

C macro references are erroneously written using :c:macro:: (note the
double colon). This causes the references to be outputted as combination
of verbatim roles and italicized names instead.

Correct the syntax.

Fixes: dce548889650c1 ("Documentation: Add TI TPS6594 PFSM")
Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20251104041812.31402-4-bagasdotme@gmail.com>