[DAGTypeLegalizer] Add missing BR_CC handler for soft-promoted half operands (#196214)
`SoftPromoteHalfOperand` had no case for `ISD::BR_CC`, causing a crash
when a half-typed `fcmp` result fed directly into a conditional branch.
All other comparison-related nodes (`SETCC, SELECT_CC`) were already
handled. Add `SoftPromoteHalfOp_BR_CC` following the same pattern as
`SoftPromoteHalfOp_SELECT_CC`.
Fixes #195562
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Co-authored-by: Tony Varghese <tony.varghese@ibm.com>