fix flushing of buffer beyond the range

while flushing tz_buf, the end of buffer is miscalculated.
tz_buz is unsigned int pointer so tz_buf+PAGE_ALIGN(size_pwrlevels)
will actually points after 4*PAGE_ALIGN(size_pwrlevels) bytes.
so it will flush more pages. if those additional pages are
not mapped in MMU it causes panic.

CRs-Fixed: 990681
Change-Id: I6b9f78ce3faca9b890d6766904605c22b21dd44d
Signed-off-by: Srinivasarao P <spathi@codeaurora.org>