s390/pkey/zcrypt: spelling s/crytp/crypt/

Fix typos in a comments.

Link: https://lkml.kernel.org/r/20200212084622.9219-1-geert+renesas@glider.be
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
