spi: Move freescale-specific code into a private header

At present there are two SPI functions only used by freescale which are
defined in the spi_flash.h header. One function name matches an existing
generic SPL function.

Move these into a private header to avoid confusion.

Arcturus looks like it does not actually support SPI, so drop the SPI code
from that board.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/board/freescale/common/spl.h b/board/freescale/common/spl.h
new file mode 100644
index 0000000..88c987e
--- /dev/null
+++ b/board/freescale/common/spl.h
@@ -0,0 +1,13 @@
+/*
+ * Copyright 2016 Google, Inc
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#ifndef __FREESCALE_BOARD_SPL_H
+#define __FREESCALE_BOARD_SPL_H
+
+void fsl_spi_spl_load_image(uint32_t offs, unsigned int size, void *vdst);
+void fsl_spi_boot(void) __noreturn;
+
+#endif