Fix handling of cudaDeviceEnablePeerAccess return value

[anvishwa-amd]

Problem

When building PyTorch on AMD ROCm the build reported a warning for hipDeviceEnablePeerAccess().

/home/anvishwa/src/pytorch/build/third_party/gloo/hip/gloo/hip_collectives_native.h:86:9: warning: ignoring return value of type 'hipError_t' declared with 'nodiscard' attribute [-Wunused-value]
86 |         hipDeviceEnablePeerAccess(devB, 0);

Summary

Handle the return value of cudaDeviceEnablePeerAccess correctly instead of using cudaGetLastError().
cudaDeviceEnablePeerAccess is a synchronous host API. Its return value already reflects the call result, so cudaGetLastError() is unnecessary and can return stale errors from earlier async work.

Signature

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__host__​cudaError_t cudaDeviceEnablePeerAccess ( int peerDevice, unsigned int flags )
Enables direct access to memory allocations on a peer device.

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The change is nominal and resolves the build warning while keeping the same behavior.

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[anvishwa-amd]

@kapilsh Can you please have a look at it. Thank you !

[anvishwa-amd]

@kapilsh Can you please have a look at it. Thank you !

Thanks @kapilsh for triggering the CI, I see unrelated failures in this can we retry ?