ANVL: Fixes to boot from eMMC on modified board

These are needed for MLO to boot.
ANVL: Generate install image dynamically depending on the boot options

We're currently wasting space with the various padded images. Let's just
generate the install image out of the components needed for the install.
ANVL: Update USB gadget name

Use Anvl as suggested by Liam.
ANVL: Erase the whole NAND if erase is specified

This is quite fast, so might as well erase the whole
chip to avoid accidentally loading some old kernel.
ANVL: Remove old huge binaries

These are no longer needed as the install image gets generated
dynamically.
ANVL: Update binaries for booting from eMMC

This now also works on modified boards to boot from eMMC.
The unmodified boards work also booting from NAND for u-boot,
then using eMMC for kernel and initramfs. Ended up updating
u-boot while debugging initramfs not working from eMMC.

U-boot: 46528b1851d990b8d9052071010c22a653fbdbc4
Kernel: a7ab20d81dd16e7e49e38956ccc7c017deb684bb
Initramfs: 314284500e4ef080e7f6b829c647fd32e4d8b700