sparc64: add __{get,put}_kernel_nofault()

sparc64 is one of the architectures that uses separate address
spaces for kernel and user addresses, so __get_kernel_nofault()
can not just call into the normal __get_user() without the
access_ok() check.

Instead duplicate __get_user() and __put_user() into their
in-kernel versions, with minor changes for the calling conventions
and leaving out the address space modifier on the assembler
instruction.

This could surely be written more elegantly, but duplicating it
gets the job done.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>