remove nvme support from the "default" grub tree
now there are three trees:
* default: no xhci or nvme patches
* nvme: contains nvme support
* xhci: contains xhci and nvme support
this is in case a bug like lbmk issue #216 ever occurs
again, as referenced before during lbmk audit 5
there is no indication that the nvme patch causes any
issues, but after previous experience i want to be sure
Signed-off-by: Leah Rowe <leah@libreboot.org>