felboot: Reduce _start to just a call to s_init.
felboot: Even closer to u-boot
Revert "felboot: Reuse sunxi_board_init() directly from u-boot tree"

For some reason cubieboard no longer works with this. a13-olinuxino do
work however. Needs further analysis.

This reverts commit de093ee7eff417e188b3c60c1dc1d574c9a546ac.

Conflicts:
	felboot/main.c