net/mlx5: Fix FPGA capability location

Currently, FPGA capability is located in (mdev)->caps.hca_cur,
change the location to be (mdev)->caps.fpga,
since hca_cur is reserved for HCA device capabilities.

Fixes: e29341fb ("net/mlx5: FPGA, Add basic support for Innova")
Signed-off-by: Inbar Karmy <inbark@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>