geom_ctl.c: remove stale header files

- Remove "opt_geom.h", no kernel options are used.

- Remove <sys/sysctl.h>, no sysctl functionality is used here.

- Remove <sys/bio.h>, requirements for bio moved out in r112534.

- Remove <sys/lock.h> and <sys/mutex.h>, last used by DROP_GIANT() and
  PICKUP_GIANT(), which were removed in r115624.

- Remove <sys/disk.h> and <sys/kernel.h>, not used.

Reviewed by: phk, kevans (mentor)
Approved by: phk, kevans (mentor)
Differential Revision: https://reviews.freebsd.org/D26805

sys/geom/geom_ctl.c

@@ -38,22 +38,12 @@
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
-#include "opt_geom.h"
-
 #include <sys/param.h>
 #include <sys/systm.h>
-#include <sys/kernel.h>
-#include <sys/sysctl.h>
-#include <sys/bio.h>
 #include <sys/conf.h>
-#include <sys/disk.h>
 #include <sys/malloc.h>
-#include <sys/sysctl.h>
 #include <sys/sbuf.h>
 
-#include <sys/lock.h>
-#include <sys/mutex.h>
-
 #include <vm/vm.h>
 #include <vm/vm_extern.h>