touchscreen: Remove dependency to libgdbus from libsyscommon

touchscreen: Remove dependency to libgdbus from libsyscommon

The libsyscommon dependencies were not organized and the libgdbus headers were used
without being hidden.
It is not advisable to reference header files with unspecified dependencies and
expose them in header file.
libgdbus header caused unnecessary addition of libsyscommon dependencies.
To use touchscreen header without libsyscommon dependency and remove
dbus_pending_cb callback type usage, touchscreen_pending_cb is added.
Also libgdbus inclusion is removed.

Change-Id: I441e6a29b6d25b1018f8a12d81073897193ee47f
Signed-off-by: Yunhee Seo <yuni.seo@samsung.com>