spi_qsd: Add vote for clock path

Currently the spi driver votes for its core clock. However, it is
possible that the core-clock's source will be off. When the source
is off, the spi core is not clocked. This patch adds voting for
the entire clock path, thus guarantee clocking to the spi core.
Voting for the path cost a few msecs. A client may choose when
to pay this overhead. By default the votes takes place in the
runtime-pm callbacks which tie to transaction requests. A client
may choose to invoke these callbacks itself whenever it likes
by directly calling the driver's runtime-pm. A third option is
to set the active_only flag in platform data which results in the
callbacks being called when the application processor power state
changes.

CRs-Fixed: 478465
Change-Id: Ib866399c0e84a875a19a0d1506d77bbe77d5fe61
Signed-off-by: Gilad Avidov <gavidov@codeaurora.org>