dump: Rework dump_calculate_size function

dump: Rework dump_calculate_size function

dump_calculate_size() sums up all the sizes of the guest memory
blocks. Since we already have a function that calculates the size of a
single memory block (dump_get_memblock_size()) we can simply iterate
over the blocks and use the function instead of calculating the size
ourselves.

Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com>
Message-Id: <20220811121111.9878-7-frankja@linux.ibm.com>