uaccess: drop pointless ifdefs

None of those file is ever included from uapi stuff, so __KERNEL__
is always defined.  None of them is ever included from assembler
(they are only pulled from linux/uaccess.h, which _can't_ be
included from assembler), so __ASSEMBLY__ is never defined.

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