spi: pxa2xx: Update header block in pxa2xx_ssp.h

We have direct users of some headers that are missed and
have header included when forward declarations are enough.

Update header block in pxa2xx_ssp.h to align with actual usage.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200826151455.55970-1-andriy.shevchenko@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

include/linux/pxa2xx_ssp.h

@@ -16,10 +16,15 @@
 #ifndef __LINUX_SSP_H
 #define __LINUX_SSP_H
 
-#include <linux/list.h>
+#include <linux/compiler_types.h>
 #include <linux/io.h>
-#include <linux/of.h>
+#include <linux/kconfig.h>
+#include <linux/list.h>
+#include <linux/types.h>
 
+struct clk;
+struct device;
+struct device_node;
 
 /*
  * SSP Serial Port Registers