[params] Rename "form parameter" to "request parameter"

Prepare for the parameter mechanism to be generalised to specifying
request parameters that are passed via mechanisms other than an
application/x-www-form-urlencoded form.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/core/parseopt.c

@@ -302,7 +302,7 @@ int parse_autovivified_setting ( char *text, struct named_setting *setting ) {
 }
 
 /**
- * Parse form parameter list name
+ * Parse request parameter list name
  *
  * @v text		Text
  * @ret params		Parameter list