cnss: Populate dump table only for dynamic memory

Dump table needs to be populated only if the RAMDUMP memory is
allocated dynamically. Check before register with dump table.

Change-Id: I45c2725c858d4cdb1ae12c1b05b4b8c4085689e5
Signed-off-by: Prashanth Bhatta <bhattap@codeaurora.org>
CRs-fixed: 748596