Revert "usb: get rid of Samsung customization"

Windows can't correctly recognize the device and makes RNDIS unusable.

This reverts commit e984f70a82d4b79530392bbc665e61c80a5a17e8.
drivers: usb: gadget: re-enable adb once rndis is disabled
initramfs: don't create /emmc

It's not always needed and doesn't allow the creation of the symlink to
/storage/sdcard1, needed for backward compatibility.