GKI cleanup - moved GKI buffer allocation wrappers to OSI

* Moved the following GKI buffer allocation functions to OSI:
  - GKI_getbuf() -> osi_getbuf()
  - GKI_freebuf() -> osi_freebuf()
  - GKI_get_buf_size() -> osi_get_buf_size()

  For now we need the osi_getbuf() / osi_freebuf() allocation wrapper,
  because we need to be able to call osi_get_buf_size() on the allocated
  buffer.
  In the future those should be replaced with osi_malloc() / osi_free().
  Currently, the osi_malloc() buffer size internal allocation tracker
 does not always track the size, hence we need the osi_getbuf() wrapper.

* Replaced GKI_MAX_BUF_SIZE with BT_DEFAULT_BUFFER_SIZE

* Added new file include/bt_common.h that can be usee to include
  few files that should be included alost everywhere (e.g. bt_target.h"
  NOTE: This file might be removed in the future and we should include
  everywhere the right set of header files.

* Removed some of the GKI-related references

* Removed file include/gki_target.h

Change-Id: Ie87830e73143de200746d54235aa99f228a95024
diff --git a/btif/src/btif_core.c b/btif/src/btif_core.c
index 9408a4f..7b29399 100644
--- a/btif/src/btif_core.c
+++ b/btif/src/btif_core.c
@@ -62,7 +62,7 @@
 #include "btif_util.h"
 #include "btu.h"
 #include "device/include/controller.h"
-#include "gki.h"
+#include "bt_common.h"
 #include "osi/include/fixed_queue.h"
 #include "osi/include/future.h"
 #include "osi/include/log.h"
@@ -210,7 +210,7 @@
     BTIF_TRACE_VERBOSE("btif_transfer_context event %d, len %d", event, param_len);
 
     /* allocate and send message that will be executed in btif context */
-    if ((p_msg = (tBTIF_CONTEXT_SWITCH_CBACK *) GKI_getbuf(sizeof(tBTIF_CONTEXT_SWITCH_CBACK) + param_len)) != NULL)
+    if ((p_msg = (tBTIF_CONTEXT_SWITCH_CBACK *) osi_getbuf(sizeof(tBTIF_CONTEXT_SWITCH_CBACK) + param_len)) != NULL)
     {
         p_msg->hdr.event = BT_EVT_CONTEXT_SWITCH_EVT; /* internal event */
         p_msg->p_cb = p_cback;
@@ -308,7 +308,7 @@
       BTIF_TRACE_ERROR("unhandled btif event (%d)", p_msg->event & BT_EVT_MASK);
       break;
   }
-  GKI_freebuf(p_msg);
+  osi_freebuf(p_msg);
 }
 
 /*******************************************************************************