Add support for the SDX55 SoC, which includes IPA version 4.5.

Starting with IPA v4.5, a few of the memory regions have a different
number of "canary" values; update comments in the where the region
identifers are defined to accurately reflect that.

I'll note three differences in SDX55 versus the other two existing
platforms (SDM845 and SC7180):
  - SDX55 uses a 32-bit Linux kernel
  - SDX55 has four interconnects rather than three
  - SDX55 uses IPA v4.5, which uses inline checksum offload
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>