lib/bdev: spdk_bdev_open_ext() returns -ENODEV if bdev whose name matches is not found

For example, for pass-through bdev modules, it is acceptable that
bdev whose name matches is not found when creating a pass-through
bdev.

The next patch will replace spdk_bdev_open() by spdk_bdev_open_ext()
for pass-through bdev module.

spdk_bdev_open_ext() includes spdk_bdev_get_by_name(). Pass-through
bdev module has to know if spdk_bdev_get_by_name() returned NULL
in spdk_bdev_open_ext().

Hence change spdk_bdev_open_ext() to return -ENODEV if spdk_bdev_get_by_name()
returned NULL.

Signed-off-by: Shuhei Matsumoto <shuhei.matsumoto.xt@hitachi.com>
Change-Id: I525a7118481586161bd0e8c07b96a887c0a04210
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/4575


Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Changpeng Liu <changpeng.liu@intel.com>
Reviewed-by: Paul Luse <paul.e.luse@intel.com>
Reviewed-by: Aleksey Marchuk <alexeymar@mellanox.com>
Community-CI: Mellanox Build Bot