device/oprom/yabel: Fix spelling of *successful*

Remove one *l* at the end.

Change-Id: Ife5af64b380dc5d31f22873f1639382d2bf9a5d9
Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
Reviewed-on: https://review.coreboot.org/25748
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin Roth <martinroth@google.com>

src/device/oprom/yabel/vbe.c

@@ -82,7 +82,7 @@ vbe_prepare(void)
 	M.x86.R_EDI = 0x0;
 	M.x86.R_ES = VBE_SEGMENT;
 
-	return 0;		// successfull init
+	return 0;		// successful init
 }
 
 // VBE Function 00h