s390: drop "select HAVE_GET_USER_PAGES_FAST"

There is no Kconfig symbol named HAVE_GET_USER_PAGES_FAST. The select
statement for that symbol is a nop. Drop it.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>