wifi: iwlwifi: do not log undefined DRAM buffers unnecessarily

DRAM buffers that are not defined in the TLVs (or are unused in the
preset) would cause a log message. To avoid confusion, skip processing
buffers with an invalid (i.e. uninitialized) DRAM path.

This further reduces the noise of the message in cases where it is
unlikely to be helpful. Also update a related debug log string to better
describe what is happening.

Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230531194629.ecae60cf2d7f.Ib44a94d4aeb55dbb2e52edea8b69a09bc0f722c3@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>