SPI slave: Prototype for MCU-specific slave initialization function removed from spi_slave.h

arch @ 8e91d976

-Subproject commit 8697021d58fc05c6d047e62230e1573a45fb969a
+Subproject commit 8e91d976b4390ccf28a5f03d3a29c25c2a8c0b29

configs @ bea7a607

-Subproject commit 0e5857f50fc0033b25013f5027f4c83db8106161
+Subproject commit bea7a607db96fad3dc7871f4ff12b5a37f44c1d3

include/nuttx/spi/slave.h

@@ -269,14 +269,19 @@
  *    slave device and the SPI slave controller hardware.  This interface
  *    is implemented by the SPI slave device controller lower-half driver
  *    and is provided to the the SPI slave device driver when that driver
- *    is initialized.  That SPI slave device initialization function has
- *    the prototype:
+ *    is initialized.  That SPI slave device initialization function is
+ *    unique to the SPI slave implementation.  The prototype is probably
+ *    something like:
  *
- *      FAR struct spi_sctrlr_s *up_spi_slave_initialize(int port);
+ *      FAR struct spi_sctrlr_s *xyz_spi_slave_initialize(int port);
  *
  *    Given an SPI port number, this function returns an instance of the
  *    SPI slave controller interface.
  *
+ *    The actual prototype and more detailed usage instructions should
+ *    appear in a header file associated with the specific SPI slave
+ *    implementation.
+ *
  * 2) struct spi_sdev_s:  Defines the second interface between the SPI
  *    slave device and the SPI slave controller hardware.  This interface
  *    is implemented by the SPI slave device.  The slave device passes this
@@ -504,23 +509,6 @@ extern "C"
  * Public Functions
  ****************************************************************************/
 
-/****************************************************************************
- * Name: up_spi_slave_initialize
- *
- * Description:
- *   Initialize the selected SPI port in slave mode.
- *
- * Input Parameter:
- *   port - Chip select number identifying the "logical" SPI port.  Includes
- *          encoded port and chip select information.
- *
- * Returned Value:
- *   Valid SPI device structure reference on success; a NULL on failure
- *
- ****************************************************************************/
-
-FAR struct spi_sctrlr_s *up_spi_slave_initialize(int port);
-
 #undef EXTERN
 #if defined(__cplusplus)
 }