uaccess: add generic __{get,put}_kernel_nofault

Nine architectures are still missing __{get,put}_kernel_nofault:
alpha, ia64, microblaze, nds32, nios2, openrisc, sh, sparc32, xtensa.

Add a generic version that lets everything use the normal
copy_{from,to}_kernel_nofault() code based on these, removing the last
use of get_fs()/set_fs() from architecture-independent code.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/arm/include/asm/uaccess.h

@@ -476,8 +476,6 @@ do {									\
 	: "r" (x), "i" (-EFAULT)				\
 	: "cc")
 
-#define HAVE_GET_KERNEL_NOFAULT
-
 #define __get_kernel_nofault(dst, src, type, err_label)			\
 do {									\
 	const type *__pk_ptr = (src);					\