net: Remove redundant variable declaration in __dev_change_flags()

The old_flags variable is declared twice in __dev_change_flags(),
causing a shadow variable warning. This patch fixes the issue by
removing the redundant declaration, reusing the existing old_flags
variable instead.

	net/core/dev.c:9225:16: warning: declaration shadows a local variable [-Wshadow]
	9225 |                 unsigned int old_flags = dev->flags;
	|                              ^
	net/core/dev.c:9185:15: note: previous declaration is here
	9185 |         unsigned int old_flags = dev->flags;
	|                      ^
	1 warning generated.

Remove the redundant inner declaration and reuse the existing old_flags
variable since its value is not needed outside the if block, and it is
safe to reuse the variable. This eliminates the warning while
maintaining the same functionality.

Signed-off-by: Breno Leitao <[email protected]>
Reviewed-by: Mateusz Polchlopek <[email protected]>
Reviewed-by: Kalesh AP <[email protected]>
Reviewed-by: Nicolas Dichtel <[email protected]>
Reviewed-by: Andrew Lunn <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: leitao

net/core/dev.c

@@ -9182,7 +9182,7 @@ int __dev_change_flags(struct net_device *dev, unsigned int flags,
 
 	if ((flags ^ dev->gflags) & IFF_PROMISC) {
 		int inc = (flags & IFF_PROMISC) ? 1 : -1;
-		unsigned int old_flags = dev->flags;
+		old_flags = dev->flags;
 
 		dev->gflags ^= IFF_PROMISC;