zlib/gunzip: Use WATCHDOG_RESET macro

As usually done in U-Boot, the watchdog_reset code is called via a
macro (WATCHDOG_RESET). In zlib.c this was done differently, by using
a function pointer which is initialized with WATCHDOG_RESET upon watchdog
usage or with NULL otherwise. This patch now uses the plain
WATCHDOG_RESET macros to call the function resulting in slightly smaller
U-Boot images and simpler code.

U-Boot code size reduction:

PowerPC board with watchdog support (lwmon5):
-> 80 bytes smaller image size

PowerPC board without watchdog support (sequoia):
-> 112 bytes smaller image size

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Detlev Zundel <dzu@denx.de>
Cc: Wolfgang Denk <wd@denx.de>
Acked-by: Detlev Zundel <dzu@denx.de>
diff --git a/lib/zlib.c b/lib/zlib.c
index 26e5af1..2b31dba 100644
--- a/lib/zlib.c
+++ b/lib/zlib.c
@@ -29,6 +29,7 @@
 #include <common.h>
 #include <compiler.h>
 #include <asm/unaligned.h>
+#include <watchdog.h>
 #include "u-boot/zlib.h"
 #undef	OFF				/* avoid conflicts */
 
@@ -1075,8 +1076,7 @@
     state->hold = 0;
     state->bits = 0;
     state->lencode = state->distcode = state->next = state->codes;
-    if (strm->outcb != Z_NULL)
-	(*strm->outcb)(Z_NULL, 0);
+    WATCHDOG_RESET();
     Tracev((stderr, "inflate: reset\n"));
     return Z_OK;
 }
@@ -1776,8 +1776,7 @@
             Tracev((stderr, "inflate:       codes ok\n"));
             state->mode = LEN;
         case LEN:
-            if (strm->outcb != Z_NULL) /* for watchdog (U-Boot) */
-                (*strm->outcb)(Z_NULL, 0);
+	    WATCHDOG_RESET();
             if (have >= 6 && left >= 258) {
                 RESTORE();
                 inflate_fast(strm, out);
@@ -1990,8 +1989,7 @@
         return Z_STREAM_ERROR;
     state = (struct inflate_state FAR *)strm->state;
     if (state->window != Z_NULL) {
-	if (strm->outcb != Z_NULL)
-		(*strm->outcb)(Z_NULL, 0);
+	WATCHDOG_RESET();
 	ZFREE(strm, state->window);
     }
     ZFREE(strm, strm->state);