spi: Add error checking for invalid bus widths

At present an invalid bus width prints a message but does not return an
error. This is the opposite of the correct behaviour. Adjust it to avoid
code bloat in the common case, and avoid hard-to-debug failure in the
uncommon case.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Jagan Teki <jagan@openedev.com>

drivers/spi/spi-uclass.c

@@ -418,7 +418,7 @@ int spi_slave_ofdata_to_platdata(const void *blob, int node,
 		mode |= SPI_TX_QUAD;
 		break;
 	default:
-		error("spi-tx-bus-width %d not supported\n", value);
+		warn_non_spl("spi-tx-bus-width %d not supported\n", value);
 		break;
 	}
 
@@ -433,7 +433,7 @@ int spi_slave_ofdata_to_platdata(const void *blob, int node,
 		mode |= SPI_RX_QUAD;
 		break;
 	default:
-		error("spi-rx-bus-width %d not supported\n", value);
+		warn_non_spl("spi-rx-bus-width %d not supported\n", value);
 		break;
 	}