table: fix next hop table entry type

Change type of nht field from uint32_t to uint8_t and increase max of
next hops.

nht_entry and nht should be declared as uint8_t because
entry_size is in bytes and is given as a parameter to compute
the position in nht array.

Fixes: dc81ebbacaeb ("lpm: extend IPv4 next hop field")

Signed-off-by: Michal Kobylinski <michalx.kobylinski@intel.com>
Acked-by: Cristian Dumitrescu <cristian.dumitrescu@intel.com>