batman-adv: Fix build with kernel 5.15.38

batman-adv: Fix build with kernel 5.15.38

The build failed in this kernel due to some missing implicit includes:

  build_dir/target-aarch64_cortex-a53_musl/linux-mediatek_mt7622/batman-adv-2022.1/compat-hacks.h:64:42: warning: 'struct sk_buff' declared inside parameter list will not be visible outside of this definition or declaration
     64 | static inline int batadv_netif_rx(struct sk_buff *skb)
        |                                          ^~~~~~~
  build_dir/target-aarch64_cortex-a53_musl/linux-mediatek_mt7622/batman-adv-2022.1/compat-hacks.h: In function 'batadv_netif_rx':
  build_dir/target-aarch64_cortex-a53_musl/linux-mediatek_mt7622/batman-adv-2022.1/compat-hacks.h:66:13: error: implicit declaration of function 'in_interrupt' [-Werror=implicit-function-declaration]
    66 |         if (in_interrupt())
        |             ^~~~~~~~~~~~
  build_dir/target-aarch64_cortex-a53_musl/linux-mediatek_mt7622/batman-adv-2022.1/compat-hacks.h:67:24: error: implicit declaration of function 'netif_rx' [-Werror=implicit-function-declaration]
     67 |                 return netif_rx(skb);
        |                        ^~~~~~~~
  build_dir/target-aarch64_cortex-a53_musl/linux-mediatek_mt7622/batman-adv-2022.1/compat-hacks.h:69:24: error: implicit declaration of function 'netif_rx_ni' [-Werror=implicit-function-declaration]
     69 |                 return netif_rx_ni(skb);
        |                        ^~~~~~~~~~~
  In file included from <command-line>:
  ./include/linux/netdevice.h: At top level:
  build_dir/target-aarch64_cortex-a53_musl/linux-mediatek_mt7622/batman-adv-2022.1/compat-hacks.h:71:18: error: conflicting types for 'batadv_netif_rx'; have 'int(struct sk_buff *)'
     71 | #define netif_rx batadv_netif_rx
        |                  ^~~~~~~~~~~~~~~
  ./include/linux/netdevice.h:4029:5: note: in expansion of macro 'netif_rx'
   4029 | int netif_rx(struct sk_buff *skb);
        |     ^~~~~~~~
  build_dir/target-aarch64_cortex-a53_musl/linux-mediatek_mt7622/batman-adv-2022.1/compat-hacks.h:64:19: note: previous definition of 'batadv_netif_rx' with type 'int(struct sk_buff *)'
     64 | static inline int batadv_netif_rx(struct sk_buff *skb)
        |                   ^~~~~~~~~~~~~~~
  cc1: some warnings being treated as errors

Reported-by: Chen Minqiang <ptpt52@gmail.com>
Fixes: b65a8ca03aec ("batman-adv: update to version 2022.1")
Signed-off-by: Sven Eckelmann <sven@narfation.org>