diag: Add HSIC communication support

Add support for relaying the MDM 9k diag traffic over HSIC
to the USB DIAG MDM channel and vice versa. Also modify usb
diag_bridge to use signed parameters for buffer sizes. This
is especially needed for the final parameter of the read
and write callbacks, wherein a negative errno value may be
passed to convey an error.

Change-Id: Ifa516356a5d72597d82929a56d714f8dfb2964de
Signed-off-by: Dixon Peterson <dixonp@codeaurora.org>
diff --git a/drivers/usb/misc/diag_bridge.c b/drivers/usb/misc/diag_bridge.c
index 017ee8a..88a5993 100644
--- a/drivers/usb/misc/diag_bridge.c
+++ b/drivers/usb/misc/diag_bridge.c
@@ -86,7 +86,7 @@
 			urb->status < 0 ? urb->status : urb->actual_length);
 }
 
-int diag_bridge_read(char *data, size_t size)
+int diag_bridge_read(char *data, int size)
 {
 	struct urb		*urb = NULL;
 	unsigned int		pipe;
@@ -153,7 +153,7 @@
 			urb->status < 0 ? urb->status : urb->actual_length);
 }
 
-int diag_bridge_write(char *data, size_t size)
+int diag_bridge_write(char *data, int size)
 {
 	struct urb		*urb = NULL;
 	unsigned int		pipe;