remoteproc: qcom: mdt_loader: Don't overwrite firmware object

commit 3e8b571a9a0881ba3381ca0915995696da145ab8 upstream.

The "fw" firmware object is passed from the remoteproc core and should
not be overwritten, as that results in leaked buffers and a double free
of the the last firmware object.

Fixes: 051fb70f ("remoteproc: qcom: Driver for the self-authenticating Hexagon v5")
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>