[CHERRY-PICK] NetworkPkg/SnpDxe: Fix Snp used uninitialized

Ensures the Snp Structure is initialized as NULL.

Signed-off-by: Eeshan Londhe <[email protected]>

Author: eeshanl

NetworkPkg/SnpDxe/Snp.c

@@ -324,6 +324,8 @@ SimpleNetworkDriverStart (
 
   DEBUG ((DEBUG_NET, "\nSnpNotifyNetworkInterfaceIdentifier()  "));
 
+  Snp = NULL;
+
   Status = gBS->OpenProtocol (
                   Controller,
                   &gEfiDevicePathProtocolGuid,