virtio-mem: Correct format specifier mismatch for RISC-V

virtio-mem: Correct format specifier mismatch for RISC-V

This likely affects other, less popular host architectures as well.
Less common host architectures under linux get QEMU_VMALLOC_ALIGN (from
which VIRTIO_MEM_MIN_BLOCK_SIZE is derived) define to a variable of
type uintptr, which isn't compatible with the format specifier used to
print a user message. Since this particular usage of the underlying data
seems unique to this file, the simple fix is to just cast
QEMU_VMALLOC_ALIGN to uint32_t, which corresponds to the format specifier
used.

Signed-off-by: Bruce Rogers <brogers@suse.com>
Message-Id: <20200730130519.168475-1-brogers@suse.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>