Move error macros from <asm-generic/errno.h> to <linux/errno.h>

Move error macros from <asm-generic/errno.h> to <linux/errno.h>

There are no files that include <asm-generic/errno.h> any more.
Move error macro defines to include/linux/errno.h and remove
include/asm-generic/errno.h.

Going forward, please include <linux/errno.h> when you need error
macros.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>