pinctrl: lantiq: Remove unsued declaration ltq_pinctrl_unregister()

Commit 3f8c50c9b110 ("OF: pinctrl: MIPS: lantiq: implement lantiq/xway pinctrl support")
declared but never implemented it, so can be removed.

Signed-off-by: YueHaibing <[e-mail]>
Reviewed-by: Andy Shevchenko <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Linus Walleij <[e-mail]>

drivers/pinctrl/pinctrl-lantiq.h

···
 
 extern int ltq_pinctrl_register(struct platform_device *pdev,
 				   struct ltq_pinmux_info *info);
-extern int ltq_pinctrl_unregister(struct platform_device *pdev);
 #endif	/* __PINCTRL_LANTIQ_H */