samsung-i9195: fix kernel config (USB network working)

Created by: scintill

It lacked some hardware support, such as the USB switch. With this change, I was able to SSH over the USB network (not working in #1099)

I based this off of LineageOS 14.1's config file from its build root. I think we were missing the secondary config file (TARGET_KERNEL_VARIANT_CONFIG := msm8930_serrano_eur_lte_defconfig in BoardConfig.mk).