powerpc/powernv: Add OPAL_BUSY to opal_error_code()

Also export opal_error_code() so that it can be used in modules
Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/platforms/powernv/opal.c

@@ -998,6 +998,7 @@ int opal_error_code(int rc)
 
 	case OPAL_PARAMETER:		return -EINVAL;
 	case OPAL_ASYNC_COMPLETION:	return -EINPROGRESS;
+	case OPAL_BUSY:
 	case OPAL_BUSY_EVENT:		return -EBUSY;
 	case OPAL_NO_MEM:		return -ENOMEM;
 	case OPAL_PERMISSION:		return -EPERM;
@@ -1037,3 +1038,4 @@ EXPORT_SYMBOL_GPL(opal_write_oppanel_async);
 /* Export this for KVM */
 EXPORT_SYMBOL_GPL(opal_int_set_mfrr);
 EXPORT_SYMBOL_GPL(opal_int_eoi);
+EXPORT_SYMBOL_GPL(opal_error_code);