net: sysctl_net_core: Fix warning: 'one' defined but not used

Commit c48cf4f2 ("net: sysctl_net_core: check SNDBUF and RCVBUF for
min length") removed the last user of the variable 'one' leading to:

net/core/sysctl_net_core.c:26:12: warning: 'one' defined but not used [-Wunused-variable]

Fix this by deleting the variable.

Signed-off-by: Jon Medhurst <tixy@linaro.org>
Signed-off-by: Kevin Hilman <khilman@linaro.org>