RDMA/core: Free pfn_list with appropriate kvfree call

Ensure that pfn_list allocated by kvcalloc() is freed using corresponding
kvfree() function. Match memory allocation and free routines kvcalloc -> kvfree.

Fixes: 259e9bd0 ("RDMA/core: Avoid hmm_dma_map_alloc() for virtual DMA devices")
Signed-off-by: Akhilesh Patil <akhilesh@ee.iitb.ac.in>
Link: https://patch.msgid.link/aJjcPjL1BVh8QrMN@bhairav-test.ee.iitb.ac.in


Signed-off-by: Leon Romanovsky <leon@kernel.org>