Check count for 0, to avoid a potential underflow. Make the check the
same as the one in rproc_recovery_write().

Fixes: 3afdc59e ("remoteproc: Add coredump debugfs entry")
Signed-off-by: Alistair Delva <adelva@google.com>
Cc: Rishabh Bhatnagar <rishabhb@codeaurora.org>
Cc: stable@vger.kernel.org
Cc: Ohad Ben-Cohen <ohad@wizery.com>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Sibi Sankar <sibis@codeaurora.org>
Cc: linux-remoteproc@vger.kernel.org
Cc: kernel-team@android.com
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20220119232139.1125908-1-adelva@google.com