The current version of struct stat has been taken from an
ancient Linux Kernel. It looks different on different architectures
to support different userspace formats of struct stat. As we do
not have a userspace on barebox there is no need to keep different
versions.

Also, this unification make MIPS arch possible.

Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>