argv_split: fix kernel-doc warnings

Use proper kernel-doc notation to prevent build warnings:

lib/argv_split.c:36: warning: Function parameter or member 'argv' not described in 'argv_free'
lib/argv_split.c:61: warning: No description found for return value of 'argv_split'

Link: https://lkml.kernel.org/r/20230912060838.3794-1-rdunlap@infradead.org
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: rddunlap

lib/argv_split.c

@@ -28,7 +28,7 @@ static int count_argc(const char *str)
 
 /**
  * argv_free - free an argv
- * @argv - the argument vector to be freed
+ * @argv: the argument vector to be freed
  *
  * Frees an argv and the strings it points to.
  */
@@ -46,7 +46,7 @@ EXPORT_SYMBOL(argv_free);
  * @str: the string to be split
  * @argcp: returned argument count
  *
- * Returns an array of pointers to strings which are split out from
+ * Returns: an array of pointers to strings which are split out from
  * @str.  This is performed by strictly splitting on white-space; no
  * quote processing is performed.  Multiple whitespace characters are
  * considered to be a single argument separator.  The returned array