target/generic: add ttyCPMx device nodes to device_table / securetty

Serial devices for CPM cores on ppc.

target/generic/device_table.txt

@@ -72,6 +72,7 @@
 #/dev/ttySA	c	666	0	0	204	5	0	1	3
 /dev/psaux	c	666	0	0	10	1	0	0	-
 #/dev/ppp	c	666	0	0	108	0	-	-	-
+/dev/ttyCPM	c	666	0	0	204	46	0	1	4
 /dev/ttyAMA	c	666	0	0	204	64	0	1	4
 /dev/ttyPSC	c	666	0	0	204	148	0	1	4
 /dev/ttyUL	c	666	0	0	204	187	0	1	4

target/generic/target_busybox_skeleton/etc/securetty

@@ -22,3 +22,7 @@ ttyPSC0
 ttyPSC1
 ttyPSC2
 ttyPSC3
+ttyCPM0
+ttyCPM1
+ttyCPM2
+ttyCPM3

target/generic/target_skeleton/etc/securetty

@@ -22,3 +22,7 @@ ttyPSC0
 ttyPSC1
 ttyPSC2
 ttyPSC3
+ttyCPM0
+ttyCPM1
+ttyCPM2
+ttyCPM3