generic: 6.1: fix compilation warning for CONFIG_PROC_STRIPPED

generic: 6.1: fix compilation warning for CONFIG_PROC_STRIPPED

Fix compilation warning for CONFIG_PROC_STRIPPED for kernel 6.1.

Fix compilation warning:
make[4]: Leaving directory '/__w/openwrt/openwrt/openwrt/build_dir/target-mips-openwrt-linux-musl_musl/linux-ath79_tiny/linux-6.1.55'
net/ipv4/inet_timewait_sock.c: In function '__inet_twsk_schedule':
net/ipv4/inet_timewait_sock.c:272:22: error: unused variable 'kill' [-Werror=unused-variable]
  272 |                 bool kill = timeo <= 4*HZ;
      |                      ^~~~
cc1: all warnings being treated as errors

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>