param: add a free hook to kernel_param_ops.

This allows us to generalize the KPARAM_KMALLOCED flag, by calling a function
on every parameter when a module is unloaded.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Tested-by: Phil Carmody <ext-phil.2.carmody@nokia.com>

include/linux/moduleparam.h

@@ -36,6 +36,8 @@ struct kernel_param_ops {
 	int (*set)(const char *val, const struct kernel_param *kp);
 	/* Returns length written or -errno.  Buffer is 4k (ie. be short!) */
 	int (*get)(char *buffer, const struct kernel_param *kp);
+	/* Optional function to free kp->arg when module unloaded. */
+	void (*free)(void *arg);
 };
 
 /* Flag bits for kernel_param.flags */