efivars: add missing parameter to efi_pstore_read()

In the case where CONFIG_PSTORE=n, the function efi_pstore_read() doesn't have the correct list of parameters. This patch provides a definition of efi_pstore_read() with 'char **buf' added to fix this warning:
"drivers/firmware/efivars.c:609: warning: initialization from".

---
 drivers/firmware/efivars.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

index a54a6b9..b0a8117 100644
@@ -581,7 +581,8 @@ static int efi_pstore_close(struct pstore_info *psi)
 }
 
 static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
-			       struct timespec *time, struct pstore_info *psi)
+			       struct timespec *timespec,
+			       char **buf, struct pstore_info *psi)
 {
 	return -1;
 }

1.7.2.5

Thanks. Will ask Linus to pull from my tree soon - but if someone else pushes it consider it:

-Tony

[This has been broken in linux-next for over a week - I guess all linux-next builders have PSTORE=y]