msm: ipa3: pre-allocate IP_PKT_INIT

For LAN scenarios IPA driver needs to program
an immediate command before every packet. Use a pre-allocated
DMA buffer for these immediate commands instead of allocating
and DMA mapping those for each packet.

Change-Id: I63e1b3edd25ee79d5e276c1cde954bba9b22bf71
CRs-Fixed: 2022853
Acked-by: Ady Abraham <adya@qti.qualcomm.com>
Signed-off-by: Skylar Chang <chiaweic@codeaurora.org>