iommufd: viommu: free memory allocated by kvcalloc() using kvfree()

Use kvfree() instead of kfree() to free pages allocated by kvcalloc()
in iommufs_hw_queue_alloc_phys() to fix potential memory corruption.
Ensure the memory is properly freed, as kvcalloc may internally use
vmalloc or kmalloc depending on available memory in the system.

Fixes: 2238ddc2b056 ("iommufd/viommu: Add IOMMUFD_CMD_HW_QUEUE_ALLOC ioctl")
Link: https://patch.msgid.link/r/aJifyVV2PL6WGEs6@bhairav-test.ee.iitb.ac.in
Signed-off-by: Akhilesh Patil <akhilesh@ee.iitb.ac.in>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
Reviewed-by: Pranjal Shrivastava <praan@google.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>