t seems certain Intel GPUs use GPIO bitbanging over a child device
instead of GMBUS access for I2C transfers. The GMBUS driver falls back
to this mode when a transfer times out. However, the first transfer to
timeout was sending the request back to itself resulting in an panic due
to recursing on a lock. Fix it to forward the request on to the proper
device. This appears to have been accidentally changed in r277487.

Reported by: Joe Maloney <jmaloney@pcbsd.org>
Reviewed by: adrian, dumbbell, imp
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D4599