msm: pm-8x60: Modify L2 management mechanism in power collapse

Modify the L2 cache flush mechanism during Power collapse. For targets
with external L2 and TZ, L2 can only be flushed and not disabled as this
a secure operation. For targets with external L2 and no TZ kernel can flush
and disable the L2 cache. The decision on which cache flush mechanism to
use is determined by the power collapse type being exercised on that
platform.
Also modify the usage of qtimer based on target specific configuration
instead of using a socinfo based API to determine CPU type.

Signed-off-by: Girish Mahadevan <girishm@codeaurora.org>
Change-Id: Ib937c15782760cb81e19ac7093cb1c4fffd36afd