selftests: netdevsim: improve lib.sh include in peer.sh

Fix the peer.sh test to run from INSTALL_PATH.

Signed-off-by: David Wei <[email protected]>
Signed-off-by: NipaLocal <nipa@local>

Author: spikeh

tools/testing/selftests/drivers/net/netdevsim/peer.sh

@@ -1,7 +1,8 @@
 #!/bin/bash
 # SPDX-License-Identifier: GPL-2.0-only
 
-source ../../../net/lib.sh
+lib_dir=$(dirname $0)/../../../net
+source $lib_dir/lib.sh
 
 NSIM_DEV_1_ID=$((256 + RANDOM % 256))
 NSIM_DEV_1_SYS=/sys/bus/netdevsim/devices/netdevsim$NSIM_DEV_1_ID