mailbox: rename pl320-ipc specific mailbox.h

The patch 30058677 "ARM / highbank: add support for pl320 IPC"
added a pl320 IPC specific header file as a generic mailbox.h.
This file has been renamed appropriately to allow the
introduction of the generic mailbox API framework.

Acked-by: Mark Langsdorf <[e-mail]>
Cc: Rafael J. Wysocki <[e-mail]>
Signed-off-by: Suman Anna <[e-mail]>
Reviewed-by: Mark Brown <[e-mail]>
Acked-by: Arnd Bergmann <[e-mail]>

arch/arm/mach-highbank/highbank.c

···
 #include <linux/input.h>
 #include <linux/io.h>
 #include <linux/irqchip.h>
-#include <linux/mailbox.h>
+#include <linux/pl320-ipc.h>
 #include <linux/of.h>
 #include <linux/of_irq.h>
 #include <linux/of_platform.h>

drivers/cpufreq/highbank-cpufreq.c

···
 #include <linux/cpu.h>
 #include <linux/err.h>
 #include <linux/of.h>
-#include <linux/mailbox.h>
+#include <linux/pl320-ipc.h>
 #include <linux/platform_device.h>
 
 #define HB_CPUFREQ_CHANGE_NOTE	0x80000001

drivers/mailbox/pl320-ipc.c

···
 #include <linux/device.h>
 #include <linux/amba/bus.h>
 
-#include <linux/mailbox.h>
+#include <linux/pl320-ipc.h>
 
 #define IPCMxSOURCE(m)		((m) * 0x40)
 #define IPCMxDSET(m)		(((m) * 0x40) + 0x004)