Fix redundant declaration of dsl_pool_t

Remove redundant dsl_pool variable and duplicate spa_get_dsl()
call in vdev_rebuild_thread.

Signed-off-by: Akash B <akash-b@hpe.com>

Author: akashb-22

module/zfs/vdev_rebuild.c

@@ -764,15 +764,15 @@ vdev_rebuild_thread(void *arg)
 	spa_t *spa = vd->vdev_spa;
 	vdev_t *rvd = spa->spa_root_vdev;
 	int error = 0;
+	dsl_pool_t *dp = spa_get_dsl(spa);
 
 	/*
 	 * If there's a scrub in process request that it be stopped.  This
 	 * is not required for a correct rebuild, but we do want rebuilds to
 	 * emulate the resilver behavior as much as possible.
 	 */
-	dsl_pool_t *dsl = spa_get_dsl(spa);
-	if (dsl_scan_scrubbing(dsl))
-		dsl_scan_cancel(dsl);
+	if (dsl_scan_scrubbing(dp))
+		dsl_scan_cancel(dp);
 
 	spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);
 	mutex_enter(&vd->vdev_rebuild_lock);
@@ -854,7 +854,7 @@ vdev_rebuild_thread(void *arg)
 			if (zfs_range_tree_space(msp->ms_allocating[j])) {
 				mutex_exit(&msp->ms_lock);
 				mutex_exit(&msp->ms_sync_lock);
-				txg_wait_synced(dsl, 0);
+				txg_wait_synced(dp, 0);
 				mutex_enter(&msp->ms_sync_lock);
 				mutex_enter(&msp->ms_lock);
 				break;
@@ -931,7 +931,6 @@ vdev_rebuild_thread(void *arg)
 
 	spa_config_enter(spa, SCL_CONFIG, FTAG, RW_READER);
 
-	dsl_pool_t *dp = spa_get_dsl(spa);
 	dmu_tx_t *tx = dmu_tx_create_dd(dp->dp_mos_dir);
 	VERIFY0(dmu_tx_assign(tx, DMU_TX_WAIT | DMU_TX_SUSPEND));