tools/tests: fix resource test build on FreeBSD

error.h is not a standard header, and none of the functions declared
there are actually used by the code. This fixes the build on FreeBSD
that doesn't have error.h

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>

tools/tests/resource/test-resource.c

@@ -1,6 +1,5 @@
 #include <err.h>
 #include <errno.h>
-#include <error.h>
 #include <stdio.h>
 #include <string.h>
 #include <sys/mman.h>