net/tftp.c: cosmetic: do not initialise statics to 0 or NULL

This removes the following checkpatch issue:
 - ERROR: do not initialise statics to 0 or NULL

Signed-off-by: Luca Ceresoli <luca.ceresoli@comelit.it>
Cc: Wolfgang Denk <wd@denx.de>

net/tftp.c

@@ -125,8 +125,8 @@ static unsigned short TftpBlkSizeOption = TFTP_MTU_BLOCKSIZE;
 #define MTFTP_BITMAPSIZE	0x1000
 static unsigned *Bitmap;
 static int PrevBitmapHole, Mapsize = MTFTP_BITMAPSIZE;
-static uchar ProhibitMcast = 0, MasterClient = 0;
-static uchar Multicast = 0;
+static uchar ProhibitMcast, MasterClient;
+static uchar Multicast;
 extern IPaddr_t Mcast_addr;
 static int Mcast_port;
 static ulong TftpEndingBlock; /* can get 'last' block before done..*/