Add an optional .release_mux() callback to struct pinmux_ops. Some drivers acquire additional resources in .set_mux(), such as software locks. These resources may need to be released when the mux function is no longer active. Introducing a dedicated .release_mux() callback allows drivers to clean up such resources. The callback is optional and does not affect existing drivers. Commit 2243a87d90b42 ("pinctrl: avoid duplicated calling enable_pinmux_setting for a pin") removed the .disable() callback to resolve two issues: 1. desc->mux_usecount increasing monotonically 2. Hardware glitches caused by repeated .disable()/.enable() calls Adding .release_mux() does not reintroduce those problems. The callback is intended only for releasing driver-side resources (e.g. locks) and must not modify hardware registers. Signed-off-by: Frank Li <Frank.Li@nxp.com> Signed-off-by: Linus Walleij <linusw@kernel.org>