Upstream has reworked its build system, so it now supports PREFIX and 'make
install', so use those.
Notice that the tools have also gained a sunxi- prefix, so use that as well
when installing the target variant.
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
