[PATCH -next 2/2] i2c: designware: Add support for new SoCs in AMDPSP driver

[Mark Hasemeyer]

-	/* Status field in command-response buffer is updated by PSP */
-	status = READ_ONCE(req->hdr.status);
+	if (req) {
+		/* Status field in command-response buffer is updated by PSP */
+		status = READ_ONCE(req->hdr.status);
+	} else {
+		status = psp_smn_read(PSP_MBOX_CMD_OFFSET, &status);
+		status &= ~PSP_MBOX_FIELDS_READY;
+	}

The value of the mbox cmd register is getting clobbered by the return value
from psp_smn_read. This can cause bus arbitration to fail as the driver will
think it can grab the bus when it's actually in use by the PSP.