interconnect: qcom: Fix uninitialized tcs_cmd::wait

Currently, if tcs_cmd_gen is called with commit=false, then
tcs_cmd::wait is left uninitialized. Since the tcs_cmd structures passed
to this function aren't zero-initialized, then we're left with random
wait values. This results in waiting for completion for more commands
than is necessary, depending on what's on the stack at the time.

Removing the unnecessary if-condition fixes this, but add an explicit
memset of the tcs_cmd structure as well to ensure predictable behavior
if more tcs_cmd members are added in the future.

Change-Id: Ib85f6bd76b5fa3b4295e998b2651485687a558df
Signed-off-by: Mike Tipton <mdtipton@codeaurora.org>