LU-17791 build: use external o2ib path for ko2iblnd.ko

LU-17791 build: use external o2ib path for ko2iblnd.ko

The O2IBPATH variable was split into INT_O2IBPATH used
for in-kernel o2iblnd and EXT_O2IBPATH for the external
o2iblnd driver.

Correct a case where the transtion from @O2IBPATH@ to
@EXT_O2IBPATH@ was missed when support for multiple lnds
deb packaging was initially added.

Fixes: 95287378fab ("LU-16967 build: Separate lnet LND deb packaging")
Signed-off-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Change-Id: I94ff393a437c6875cda9db266ab636fd88871188
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/54984
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Shuichi Ihara <sihara@ddn.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Reviewed-by: Shuichi Ihara <sihara@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>