man: Use CR for constant width font

With version 1.23 groff/troff disabled the non-portable font CW and
started to complain about a missing CW font when previewing some of the
man pages, with messages like

$ man --warnings cpumf/man/pai.8 > /dev/null
troff:<standard input>:244: warning: cannot select font 'CW'

Use CR to replace CW.

Closes: https://github.com/ibm-s390-linux/s390-tools/pull/187
[hoeppner@linux.ibm.com: Adapt commit message]
Signed-off-by: Dan Horák <dan@danny.cz>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

zdev/man/chzdev.8

@@ -22,7 +22,7 @@
 .  ds pfont \fP
 .  nh
 .  na
-.  ft CW
+.  ft CR
 \\$*
 .  ft \\*[pfont]
 .  ad

zdev/man/lszdev.8

@@ -22,7 +22,7 @@
 .  ds pfont \fP
 .  nh
 .  na
-.  ft CW
+.  ft CR
 \\$*
 .  ft \\*[pfont]
 .  ad