driver core: Fix handling of fw_devlink=permissive

When commit 8375e74f ("driver core: Add fw_devlink kernel
commandline option") added fw_devlink, it didn't implement "permissive"
mode correctly.

That commit got the device links flags correct to make sure unprobed
suppliers don't block the probing of a consumer. However, if a consumer
is waiting for mandatory suppliers to register, that could still block a
consumer from probing.

This commit fixes that by making sure in permissive mode, all suppliers
to a consumer are treated as a optional suppliers. So, even if a
consumer is waiting for suppliers to register and link itself (using the
DL_FLAG_SYNC_STATE_ONLY flag) to the supplier, the consumer is never
blocked from probing.

Fixes: 8375e74f

 ("driver core: Add fw_devlink kernel commandline option")
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Saravana Kannan <saravanak@google.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/20200331022832.209618-1-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>