misc: fastrpc: check qcom_scm_assign_mem() return in rpmsg_probe

In the SDSP probe path, qcom_scm_assign_mem() is used to assign the
reserved memory to the configured VMIDs, but its return value was not checked.

Fail the probe if the SCM call fails to avoid continuing with an
unexpected/incorrect memory permission configuration.

This issue was found by an in-house analysis workflow that extracts AST-based
information and runs static checks, with LLM assistance for triage, and was
confirmed by manual code review.
No hardware testing was performed.

Fixes: c3c0363bc72d4 ("misc: fastrpc: support complete DMA pool access to the DSP")
Cc: [e-mail] # 6.11-rc1
Signed-off-by: Xingjing Deng <[e-mail]>
Reviewed-by: Dmitry Baryshkov <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/misc/fastrpc.c

···
 		if (!err) {
 			src_perms = BIT(QCOM_SCM_VMID_HLOS);
 
-			qcom_scm_assign_mem(res.start, resource_size(&res), &src_perms,
+			err = qcom_scm_assign_mem(res.start, resource_size(&res), &src_perms,
 				    data->vmperms, data->vmcount);
+			if (err)
+				goto err_free_data;
 		}
 
 	}