firmware: qcom: scm: preserve assign_mem() error return value

When qcom_scm_assign_mem() fails, the error value is currently being
overwritten after it is logged, resulting in the loss of the original
error code. Fix this by retaining and returning the original error value
as intended.

Signed-off-by: Mukesh Ojha <[e-mail]>
Reviewed-by: Konrad Dybcio <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Bjorn Andersson <[e-mail]>

drivers/firmware/qcom/qcom_scm.c

···
 	if (ret) {
 		dev_err(__scm->dev,
 			"Assign memory protection call failed %d\n", ret);
-		return -EINVAL;
+		return ret;
 	}
 
 	*srcvm = next_vm;