module: don't ignore vermagic string if module doesn't have modversions

Linus found a logic bug: we ignore the version number in a module's
vermagic string if we have CONFIG_MODVERSIONS set, but modversions
also lets through a module with no __versions section for modprobe
--force (with tainting, but still).

We should only ignore the start of the vermagic string if the module
actually *has* crcs to check.  Rather than (say) having an
entertaining hissy fit and creating a config option to work around the
buggy code.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/init/Kconfig b/init/Kconfig
index 3b5adbf..6135d07 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -845,9 +845,9 @@
 	depends on MODULES
 	default n
 	help
-	  This option allows loading of modules even if that would set the
-          'F' (forced) taint, due to lack of version info.  Which is
-	  usually a really bad idea.
+	  Allow loading of modules without version information (ie. modprobe
+	  --force).  Forced module loading sets the 'F' (forced) taint flag and
+	  is usually a really bad idea.
 
 config MODULE_UNLOAD
 	bool "Module unloading"