(master) wcmConfig: fix fd_refs double-increment in wcmDevOpen()

[metux]

For the device that performs the actual open (common->fd_refs == 0),
wcmDevOpen() opened the physical fd and set common->fd_refs = 1, but
never gave that same priv its own fd via wcmSetFd(). The following
'grab the common descriptor if available' block then saw
wcmGetFd(priv) still < 0 for that same priv and ran anyway, calling
wcmSetFd() again and incrementing common->fd_refs a second time for
what is really only one logical reference.

wcmDevClose() decrements fd_refs exactly once per priv whose own fd is

= 0, so the extra increment meant fd_refs never returned to 0 on
close, leaking the underlying fd on every plug/unplug cycle.

Fix by setting the just-opened priv's own fd right where the open
happens, so the fallback block's wcmGetFd(priv) < 0 check correctly
sees it as already satisfied and skips the redundant increment.

Signed-off-by: Enrico Weigelt, metux IT consult info@metux.net