ath11k: mhi: remove state machine

State machines are difficult to understand and in this case it's just useless,
which is shown by the diffstat. So remove it entirely to make the code simpler.

No functional changes.

Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-03003-QCAHSPSWPL_V1_V2_SILICONZ_LITE-2

Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20220401173042.17467-2-kvalo@kernel.org