add asm-generic/extable.h

... and make the users of generic uaccess.h use that.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

arch/h8300/include/asm/Kbuild

@@ -13,6 +13,7 @@ generic-y += dma.h
 generic-y += emergency-restart.h
 generic-y += errno.h
 generic-y += exec.h
+generic-y += extable.h
 generic-y += fb.h
 generic-y += fcntl.h
 generic-y += ftrace.h