adapter: expose HLA interface in struct adapter_driver

The transition of STM8/SWIM out of HLA will require a new struct
swim_ops in struct adapter_driver.
To simplify the development, make the HLA interface temporarily
accessible through the struct adapter_driver.
This commit will be reverted after the swim rework.

Change-Id: I1e4f370cf64641164d7bcaa22f75ac58c9240052
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/5527
Tested-by: jenkins

src/jtag/hla/hla_interface.c

@@ -361,4 +361,7 @@ struct adapter_driver hl_adapter_driver = {
 	.poll_trace = &hl_interface_poll_trace,
 
 	/* no ops for HLA, targets hla_target and stm8 intercept them all */
+
+	/* FIXME: helper to simplify transition of HLA drivers. To be removed */
+	.hla_if = &hl_if,
 };