Suppress reporting memory leaks originating from libdevstat

Based on https://cgit.freebsd.org/src/tree/lib/libdevstat/devstat.c
the following four functions call memory allocation functions:

- devstat_getdevs()
- devstat_selectdevs()
- devstat_buildmatch()
- get_devstat_kvm()

scripts/htop_suppressions.valgrind

@@ -45,3 +45,13 @@
    fun:CRT_setColors
    fun:CRT_init
 }
+
+{
+   <devstat internal memory>
+   Memcheck:Leak
+   match-leak-kinds: possible,reachable
+   ...
+   obj:*/libdevstat*
+   ...
+   fun:Platform_getDiskIO
+}