mailbox: rename headers

Rename mailbox*.h to match the naming convention requested during review
of the new reset subsystem.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Simon Glass <sjg@chromium.org>

drivers/mailbox/mailbox-uclass.c

@@ -7,8 +7,8 @@
 #include <common.h>
 #include <dm.h>
 #include <fdtdec.h>
-#include <mailbox_client.h>
-#include <mailbox_uclass.h>
+#include <mailbox.h>
+#include <mailbox-uclass.h>
 
 DECLARE_GLOBAL_DATA_PTR;
 

drivers/mailbox/sandbox-mbox-test.c

@@ -6,7 +6,7 @@
 
 #include <common.h>
 #include <dm.h>
-#include <mailbox_client.h>
+#include <mailbox.h>
 #include <asm/io.h>
 
 struct sandbox_mbox_test {

drivers/mailbox/sandbox-mbox.c

@@ -6,7 +6,7 @@
 
 #include <common.h>
 #include <dm.h>
-#include <mailbox_uclass.h>
+#include <mailbox-uclass.h>
 #include <asm/io.h>
 #include <asm/mbox.h>