atmel_spi: Driver for the Atmel SPI controller

This adds a driver for the SPI controller found on most AT91 and AVR32
chips, implementing the new SPI API.

Changed in v4:
  - Update to new API
  - Handle zero-length transfers appropriately. The user may send a
    zero-length SPI transfer with SPI_XFER_END set in order to
    deactivate the chip select after a series of transfers with chip
    select active. This is useful e.g. when polling the status
    register of DataFlash.

Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
diff --git a/include/asm-avr32/arch-at32ap700x/clk.h b/include/asm-avr32/arch-at32ap700x/clk.h
index 4a1dd33..a9d8431 100644
--- a/include/asm-avr32/arch-at32ap700x/clk.h
+++ b/include/asm-avr32/arch-at32ap700x/clk.h
@@ -74,6 +74,12 @@
 	return get_pbb_clk_rate();
 }
 #endif
+#ifdef AT32AP700x_CHIP_HAS_SPI
+static inline unsigned long get_spi_clk_rate(unsigned int dev_id)
+{
+	return get_pba_clk_rate();
+}
+#endif
 
 extern void clk_init(void);