accel/qaic: Validate if BO is sliced before slicing

QAIC_ATTACH_SLICE_BO attaches slicing configuration to a BO. Validate if
given BO is already sliced. An already sliced BO cannot be sliced again.

Fixes: ff13be83 ("accel/qaic: Add datapath")
Signed-off-by: Pranjal Ramajor Asha Kanojiya <quic_pkanojiy@quicinc.com>
Reviewed-by: Carl Vanderlip <quic_carlv@quicinc.com>
Reviewed-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Signed-off-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230517193540.14323-3-quic_jhugo@quicinc.com