container_of: remove container_of_safe()

It came in from a staging driver that has been long removed from the
tree, and there are no in-kernel users of the macro, and it's very
dubious if anyone should ever use this thing, so just remove it
entirely.
Reviewed-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Acked-by: Rafael J. Wysocki <rafael@kernel.org>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20221024123933.3331116-1-gregkh@linuxfoundation.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/container_of.h

@@ -21,20 +21,4 @@
 		      "pointer type mismatch in container_of()");	\
 	((type *)(__mptr - offsetof(type, member))); })
 
-/**
- * container_of_safe - cast a member of a structure out to the containing structure
- * @ptr:	the pointer to the member.
- * @type:	the type of the container struct this is embedded in.
- * @member:	the name of the member within the struct.
- *
- * If IS_ERR_OR_NULL(ptr), ptr is returned unchanged.
- */
-#define container_of_safe(ptr, type, member) ({				\
-	void *__mptr = (void *)(ptr);					\
-	static_assert(__same_type(*(ptr), ((type *)0)->member) ||	\
-		      __same_type(*(ptr), void),			\
-		      "pointer type mismatch in container_of_safe()");	\
-	IS_ERR_OR_NULL(__mptr) ? ERR_CAST(__mptr) :			\
-		((type *)(__mptr - offsetof(type, member))); })
-
 #endif	/* _LINUX_CONTAINER_OF_H */