param: Fix duplicate module prefixes

Instead of insisting each new module_param sysfs entry is unique, handle the case where it already exists (for builtin modules).

The current code assumes that all identical prefixes are together in the section: true for normal uses, but not necessarily so if someone overrides MODULE_PARAM_PREFIX. More importantly, it's not true with the new "core_param()" code which uses "kernel" as a prefix.

This simplifies the caller for the builtin case, at a slight loss of efficiency (we do the lookup every time to see if the directory exists).

---
 include/linux/module.h |    2 
 kernel/params.c        |  253 ++++++++++++++++++++++++++-----------------------
 2 files changed, 138 insertions(+), 117 deletions(-)

diff -r 0bdb21ee0640 include/linux/module.h
@@ -59,6 +59,7 @@ struct module_kobject
 	struct kobject kobj;
 	struct module *mod;
 	struct kobject *drivers_dir;
+	struct module_param_attrs *mp;
 };
 
 /* These are either module local, or the kernel's dummy ones. */

@@ -241,7 +242,6 @@ struct module
 
 	/* Sysfs stuff. */
 	struct module_kobject mkobj;
-	struct module_param_attrs *param_attrs;
 	struct module_attribute *modinfo_attrs;
 	const char *version;
 	const char *srcversion;