net: Make table id type u32

A number of VRF patches used 'int' for table id. It should be u32 to be
consistent with the rest of the stack.

Fixes:
4e3c8992 ("net: Introduce VRF related flags and helpers")
15be405e ("net: Add inet_addr lookup by table")
30bbaa19 ("net: Fix up inet_addr_type checks")
021dd3b8 ("net: Add routes to the table associated with the device")
dc028da5 ("inet: Move VRF table lookup to inlined function")
f6d3c192

 ("net: FIB tracepoints")

Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Reviewed-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>