tz: Add msm_device_tz_log device

msm_devcie_tz_log is a debugfs module that displays
the contents of a buffer located in IMEM.  The contents
of this hold diagnostic information logged in by modules
running on secure domain.
This patch enables this tz_log debugfs module for 8x60
target devices

Change-Id: Iab64fbf19fb903991b292894807663f9bdf1a4f2
Signed-off-by: Mona Hossain <mhossain@codeaurora.org>