extlinux: pull in sys/sysmacros.h for major/minor/makedev

These functions are defined in sys/sysmacros.h, so add the include to
main.c.  This is already handled correctly in mountinfo.c.  Otherwise
we get build failures like:

main.o: In function 'find_device_sysfs':
extlinux/main.c:1131: undefined reference to 'minor'

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Gene Cumm <gene.cumm@gmail.com>

extlinux/main.c

@@ -38,6 +38,7 @@
 #include <sysexits.h>
 #include <sys/ioctl.h>
 #include <sys/stat.h>
+#include <sys/sysmacros.h>
 #include <sys/types.h>
 #include <sys/mount.h>
 #include <sys/vfs.h>