Add an API in the omap glue layer to write to the mailbox register which
can be used by comparator driver(twl). To pass the detection of the attached
device (signified by VBUS, ID) to the dwc3 core, dwc3 core has to write
to the mailbox regiter.

Signed-off-by: Kishon Vijay Abraham I <redacted>
---
 drivers/usb/dwc3/dwc3-omap.c  |   59 +++++++++++++++++++++++++++++++++++++++++
 include/linux/usb/dwc3-omap.h |   30 +++++++++++++++++++++
 2 files changed, 89 insertions(+)
 create mode 100644 include/linux/usb/dwc3-omap.h

diff --git a/drivers/usb/dwc3/dwc3-omap.c b/drivers/usb/dwc3/dwc3-omap.c
index a1704c6..7ae4d73 100644
--- a/drivers/usb/dwc3/dwc3-omap.c
+++ b/drivers/usb/dwc3/dwc3-omap.c

@@ -43,6 +43,7 @@
 #include <linux/spinlock.h>
 #include <linux/platform_device.h>
 #include <linux/platform_data/dwc3-omap.h>
+#include <linux/usb/dwc3-omap.h>
 #include <linux/pm_runtime.h>
 #include <linux/dma-mapping.h>
 #include <linux/ioport.h>

@@ -126,6 +127,8 @@ struct dwc3_omap {
 	u32			dma_status:1;
 };
 
+struct dwc3_omap		*_omap;
+
 static inline u32 dwc3_omap_readl(void __iomem *base, u32 offset)
 {
 	return readl(base + offset);

@@ -136,6 +139,56 @@ static inline void dwc3_omap_writel(void __iomem *base, u32 offset, u32 value)
 	writel(value, base + offset);
 }
 
+void omap_dwc3_mailbox(enum omap_dwc3_vbus_id_status status)