[netdrvr] tulip/winbond-840: don't let tulip.h symbol stomp ours

winbond-840 shares tulip.h with the tulip driver, because they share
many (but not all) of the same register definitions.

This is useful for the register definitions, but not helpful when it
comes to symbols that are shared among the tulip driver's C modules,
but not meant to be shared outside that one driver.

Thus, PKT_BUF_SZ is a symbol internal to tulip, but it was intruding
upon a similar symbol in winbond-840's namespace.  This was not a
problem as long as the two symbols had the same value, but upcoming
patches result in differing symbol values.
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/net/tulip/winbond-840.c

@@ -107,8 +107,6 @@ static int full_duplex[MAX_UNITS] = {-1, -1, -1, -1, -1, -1, -1, -1};
 /* Time in jiffies before concluding the transmitter is hung. */
 #define TX_TIMEOUT  (2*HZ)
 
-#define PKT_BUF_SZ		1536			/* Size of each temporary Rx buffer.*/
-
 /* Include files, designed to support most kernel versions 2.0.0 and later. */
 #include <linux/module.h>
 #include <linux/kernel.h>
@@ -137,6 +135,9 @@ static int full_duplex[MAX_UNITS] = {-1, -1, -1, -1, -1, -1, -1, -1};
 
 #include "tulip.h"
 
+#undef PKT_BUF_SZ			/* tulip.h also defines this */
+#define PKT_BUF_SZ		1536	/* Size of each temporary Rx buffer.*/
+
 /* These identify the driver base version and may not be removed. */
 static char version[] =
 KERN_INFO DRV_NAME ".c:v" DRV_VERSION " (2.4 port) " DRV_RELDATE "  Donald Becker <becker@scyld.com>\n"