slimbus: core: fix device reference leak on report present

slimbus: core: fix device reference leak on report present

Slimbus devices can be allocated dynamically upon reception of
report-present messages.

Make sure to drop the reference taken when looking up already registered
devices.

Note that this requires taking an extra reference in case the device has
not yet been registered and has to be allocated.

Fixes: 46a2bb5a7f7e ("slimbus: core: Add slim controllers support")
Cc: stable@vger.kernel.org	# 4.16
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://patch.msgid.link/20251126145329.5022-4-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>