Remove arch/${ARCH}/include/asm/errno.h

Remove arch/${ARCH}/include/asm/errno.h

Unlike Linux, nothing about errno.h is arch-specific in U-Boot.
As you see, all of arch/${ARCH}/include/asm/errno.h is just a
wrapper of <asm-generic/errno.h>.  Actually, U-Boot does not
export headers to user-space, so we just have to care about the
consistency in the U-Boot tree.

Now all of include directives for <asm/errno.h> are gone.
Deprecate <asm/errno.h>.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Alexey Brodkin <abrodkin@synopsys.com>