msm: ipa3: removed Q6 register retrieve and add new retrievals

Took out unnecessary retrieval of Q6 channel and event contexts
registers. Also added two new registers into the register retrieval
list.

Change-Id: I7aece73394e7d9fb0fadfd8b11d9dacf9d4ea5eb
CRs-Fixed: 2413750
Signed-off-by: Perry Randise <prandise@codeaurora.org>