tools/blktap2: remove unused inclusion of sys/sysctl.l

That header file is not used. Removing it would avoid build error with
musl libc, which doesn't have that header file.

Signed-off-by: Alistair Francis <alistair.francis@xilinx.com>
Reviewed-by: Doug Goldstein <cardoe@cardoe.com>
[ wei: rewrote commit message ]
Acked-by: Wei Liu <wei.liu2@citrix.com>

tools/blktap2/drivers/block-remus.c

@@ -54,7 +54,6 @@
 #include <netinet/in.h>
 #include <arpa/inet.h>
 #include <sys/param.h>
-#include <sys/sysctl.h>
 #include <unistd.h>
 #include <sys/stat.h>