[PATCH] efivars fixes

[PATCH] efivars fixes

From: Matt Domsch <Matt_Domsch@dell.com>

Patch below fixes three small bugs in efivars.c as posted by Matt Tolentino
last week and included in the latest -mm.  Aside from this small patch, I'm
quite pleased with Matt T's work, thanks!

- dummy() used for reading write-only sysfs files should return -ENODEV to
  indicate failure, not 0.

- efivar_create() should return the number of bytes written on success, not
  zero.

- efivar_delete() should return the number of bytes written on success, not
  zero.