mlxsw: minimal: Add validation for FW version

Add validation for FW version in order to prevent driver initialization
in case FW version is older than expected. FW version validation is
necessary, because use of a new field 'num_of_modules' in MGPIR register
is not backward compatible. FW 'minor' and 'subminor' versions are
expected to be greater than or equal to 2000 and 1886, respectively.

Signed-off-by: Vadim Pasternak <vadimp@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>