### What this PR does / why we need it?
This PR fixes an `AttributeError: 'Parameter' object has no attribute
'data'` that occurs when MLAPO is enabled with vLLM v0.15.0.
The error is caused by a monkey-patch on
`MLAAttention.process_weights_after_loading` which is incompatible with
changes in vLLM v0.15.0. This is likely related to PyTorch's deprecation
of the `.data` attribute on `torch.nn.Parameter` objects.
This change makes the monkey-patch conditional, so it is not applied for
vLLM v0.15.0 and newer versions, resolving the crash.
- vLLM version: v0.15.0
- vLLM main:
d7e17aaacd
Signed-off-by: Meihan-chen <jcccx.cmh@gmail.com>