module: fix memory leak when load fails after srcversion/version allocated

Normally the twisty paths of sysfs will free the attributes, but not if
we fail before we hook it into sysfs (which is the last thing we do in
load_module).

(This sysfs code is a turd, no doubt there are other issues lurking too).

Reported-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>