IB/mlx4: Fix zeroing of rnr_retry value in ib_modify_qp()

The code in __mlx4_ib_modify_qp() overwrites context->params1 after
the RNR retry parameter is ORed in, which results in the RNR retry
parameter always being set to 0.  Fix this by moving where we OR in
the value to later in the function, after the initial assignment of
context->params1.

Found by the Mellanox firmware group.

Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>