s390/zcrypt: remove set_fs() invocation in zcrypt device driver

This patch reworks the zcrypt device driver so that the set_fs()
invocation is not needed any more. Instead there is a new flag bool
userspace passed through all the functions which tells if the pointer
arguments are userspace or kernelspace. Together with the two new
inline functions z_copy_from_user() and z_copy_to_user() which either
invoke copy_from_user (userspace is true) or memcpy (userspace is
false) the zcrypt dd and the AP bus now has no requirement for
the set_fs() functionality any more.

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Reviewed-by: Ingo Franzki <ifranzki@linux.ibm.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>