platform/mellanox: mlxbf-bootctl: add NET dependency into Kconfig

The latest version of the mlxbf_bootctl driver utilizes
"sysfs_format_mac", and this API is only available if
NET is defined in the kernel configuration. This patch
changes the mlxbf_bootctl Kconfig to depend on NET.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202309031058.JvwNDBKt-lkp@intel.com/
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: David Thompson <davthompson@nvidia.com>
Link: https://lore.kernel.org/r/20230905133243.31550-1-davthompson@nvidia.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>