fix: no need to dtype A in jamba

[xgal]

What does this PR do?

Fixes # (issue)
Can't use Jamba in FSDP due to A init as FP32 no matter the weights and dtype passed. this behave isn't relevant cause the weights are BF16 and in fwd pass we anyway dtyping when needed as in mamba_2_modeling

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[ArthurZucker]

Good catch!