lrdp_V2: Fix for broken reserved_mem.py

Fix for broken reserved_mem.py in case of cma area dump.
if CONFIG_MEMORY_HOTPLUG is enabled then SECTION_SIZE_BITS is
CONFIG_HOTPLUG_SIZE_BITS else it is 30.

Signed-off-by: Ankur Bansal <ankban@codeaurora.org>
Change-Id: Iaceb6d1c0f2753d94d420e9d9f8cacff3a6b57d4