drivers: soc: qcom: Statically initialize powersave list

Calling qmi_rmnet_ps_ind_register() too early can result in NULL pointer
dereferences because the list used to store the callback structs might
not have been initialized yet.

Instead of waiting to initialize the list until qmi_rmnet_change_link()
is called with an NLMSG_CLIENT_SETUP message from userspace, we can simply
statically initialize the list so modules can register their callback
structs immediately, and start receiving notifications once the proper
indications are sent from userspace.

Change-Id: Ib5b1df5a8f9c903592d557e6a1099ccb4402bac0
Signed-off-by: Sean Tranchetti <stranche@codeaurora.org>