spi documentation: use __initdata on struct

Use __initdata for data, not __init.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/spi/spi-summary

@@ -215,7 +215,7 @@ So for example arch/.../mach-*/board-*.c files might have code like:
 	/* if your mach-* infrastructure doesn't support kernels that can
 	 * run on multiple boards, pdata wouldn't benefit from "__init".
 	 */
-	static struct mysoc_spi_data __init pdata = { ... };
+	static struct mysoc_spi_data __initdata pdata = { ... };
 
 	static __init board_init(void)
 	{