efi/efi_test: Fix uninitialized variable 'rv'

Fix minor issue found by CoverityScan:

  520        kfree(name);
  CID 1358932 (#1 of 1): Uninitialized scalar variable (UNINIT)17.
  uninit_use: Using uninitialized value rv.
  521        return rv;
  522}
Signed-off-by: Ivan Hu <ivan.hu@canonical.com>
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/20161018143318.15673-6-matt@codeblueprint.co.ukSigned-off-by: Ingo Molnar <mingo@kernel.org>

drivers/firmware/efi/test/efi_test.c

@@ -428,7 +428,7 @@ static long efi_runtime_get_nextvariablename(unsigned long arg)
 	efi_guid_t *vd = NULL;
 	efi_guid_t vendor_guid;
 	efi_char16_t *name = NULL;
-	int rv;
+	int rv = 0;
 
 	getnextvariablename_user = (struct efi_getnextvariablename __user *)arg;