gpio: Add support for microblaze xilinx GPIO

Microblaze uses gpio which is connected to the system reset.
Currently gpio subsystem wasn't used for it.

Add gpio driver and change Microblaze reset logic to be done
via gpio subsystem.

There are various configurations which Microblaze can have
that's why gpio_alloc/gpio_alloc_dual(for dual channel)
function has been introduced and gpio can be allocated
dynamically.

Adding several gpios IP is also possible and supported.

For listing gpio configuration please use "gpio status" command

This patch also remove one compilation warning:
microblaze-generic.c: In function 'do_reset':
microblaze-generic.c:38:47: warning: operation on '*1073741824u'
 may be undefined [-Wsequence-point]

Signed-off-by: Michal Simek <michal.simek@xilinx.com>

arch/microblaze/include/asm/gpio.h

@@ -1,41 +1,15 @@
 #ifndef _ASM_MICROBLAZE_GPIO_H_
 #define _ASM_MICROBLAZE_GPIO_H_
 
-#include <asm/io.h>
+#include <asm-generic/gpio.h>
 
-static inline int gpio_request(unsigned gpio, const char *label)
-{
-	return 0;
-}
+/* Allocation functions */
+extern int gpio_alloc_dual(u32 baseaddr, const char *name, u32 gpio_no0,
+			   u32 gpio_no1);
+extern int gpio_alloc(u32 baseaddr, const char *name, u32 gpio_no);
 
-static inline int gpio_free(unsigned gpio)
-{
-	return 0;
-}
+#define gpio_status()	gpio_info()
+extern void gpio_info(void);
 
-static inline int gpio_direction_input(unsigned gpio)
-{
-	return 0;
-}
-
-static inline int gpio_direction_output(unsigned gpio, int value)
-{
-	return 0;
-}
-
-static inline int gpio_get_value(unsigned gpio)
-{
-	return 0;
-}
-
-static inline int gpio_set_value(unsigned gpio, int value)
-{
-	return 0;
-}
-
-static inline int gpio_is_valid(int number)
-{
-	return 0;
-}
 #endif