RDMA/irdma: Remove redundant legacy_mode checks

RDMA/irdma: Remove redundant legacy_mode checks

The driver has the following invariants:

1. legacy_mode is only allowed on GEN_1 hardware (enforced
   in irdma_alloc_ucontext).

2. GEN_1 hardware does not set IRDMA_FEATURE_CQ_RESIZE or
   IRDMA_FEATURE_RTS_AE. These feature flags are only set
   for GEN_2 and GEN_3 hardware.

Therefore, legacy_mode is always false if IRDMA_FEATURE_CQ_RESIZE
or IRDMA_FEATURE_RTS_AE is set, so remove the redundant checks.

Link: https://patch.msgid.link/r/20260602214423.1315105-1-jmoroni@google.com
Signed-off-by: Jacob Moroni <jmoroni@google.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>