Arry of pointer to struct ffa_dev_part_info needs to be allocated to
fetch the pointers stored in XArray. However, currently we allocate the
entire structure instead of just pointers.

Fix the allocation size. This will also eliminate the below Smatch
istatic checker warning:

   |   drivers/firmware/arm_ffa/driver.c:1251 ffa_partitions_cleanup()
   |   warn: double check that we're allocating correct size: 8 vs 88
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/all/0e8ddbca-d9da-4a3b-aae3-328993b62ba2@moroto.mountain
Link: https://lore.kernel.org/r/20231031141335.3077026-1-sudeep.holla@arm.comSigned-off-by: Sudeep Holla <sudeep.holla@arm.com>