slim: msm: ngd: Add priority to DSP SSR notifier

Currently SSR framework seems to make callbacks in the order
they were registered, or based on pririties.
Due to this, APR's callback (done in its probe) may be executed
before slimbus driver's callback (only registered after children
are probed). This still works, but may take longer since codec
may try sending some disconnection commands over slimbus if APR
is notified about SSR before codec was notified by slimbus.
This failure may result in some delay in SSR handling which is
more than the KPI numbers expected for this recovery mechanism.
Priority is added to slimbus SSR notifier registration to make
sure its callback is called before APR's.

CRs-Fixed: 996871
Change-Id: Ib7f002d52310dc13b60a18972a6899ebae21ba24
Signed-off-by: Sagar Dharia <sdharia@codeaurora.org>