libefivar: Standardize #ifndef __FreeBSD__

Standardize preprocessor directives that comment out unused functions
(essentially #if 0).

No functional change intended.

Reviewed by: imp
Pull Request: https://github.com/freebsd/freebsd-src/pull/1894

lib/libefivar/efivar-dp-parse.c

@@ -313,7 +313,6 @@ GetNextDeviceNodeStr (
   return ReturnStr;
 }
 
-
 #ifndef __FreeBSD__
 /**
   Return whether the integer string is a hex string.

lib/libefivar/uefi-dplib.h

@@ -175,8 +175,7 @@ typedef struct {
 
 #pragma pack()
 
-#ifdef FreeBSD		/* Remove these on FreeBSD */
-
+#ifndef __FreeBSD__		/* Remove these on FreeBSD */
 /**
   Returns the size of a device path in bytes.