cnss2: set iova_stop to U64_MAX

When cnss2 driver is compiled as kernel loadable module,
compiler throws errors for undefined
memblock_start_of_DRAM and memblock_end_of_DRAM.

When SMMU s1 is not enabled, iova_start and iova_stop
are physical start and stop address of DDR. Thus setting
iova_stop to U64_MAX to assume all addresses are valid.

Change-Id: I910653bd45d78c8a8e78af08c277df03f9fdda01
Signed-off-by: jiad <jiad@codeaurora.org>