You can put the kernel to an SD card or into NAND, get u-boot to load
it from there, but then you would need to provide a root filesystem on
USB storage or over network. Also keep in mind that overall mainline
WM8880 support is very experimental at this stage, and crashes a lot.
Depending on your requirements, you can probably just use
WonderMedia's kernel for now, if you don't require any new kernel
features (as WonderMedia's kernel is based on 3.4.0, which is pretty
old). That you can do by writing a simple scriptcmd that loads the
existing kernel image from NAND (with nandrw command), resets the
kernel command line to something you need (including root fs location)
and boots right away.
https://groups.google.com/forum/#!msg/vt8500-wm8505-linux-kernel/_lIPr7DGANc/lDrg0_lZuPgJ