scsi: ufs: Optimize host lock on transfer requests send/compl paths

Current UFS IRQ handler is completely wrapped by host lock, and because
ufshcd_send_command() is also protected by host lock, when IRQ handler
fires, not only the CPU running the IRQ handler cannot send new requests,
the rest CPUs can neither. Move the host lock wrapping the IRQ handler into
specific branches, i.e., ufshcd_uic_cmd_compl(), ufshcd_check_errors(),
ufshcd_tmc_handler() and ufshcd_transfer_req_compl(). Meanwhile, to further
reduce occpuation of host lock in ufshcd_transfer_req_compl(), host lock is
no longer required to call __ufshcd_transfer_req_compl(). As per test, the
optimization can bring considerable gain to random read/write performance.

Link: https://lore.kernel.org/r/1621845419-14194-3-git-send-email-cang@codeaurora.org
Cc: Stanley Chu <stanley.chu@mediatek.com>
Reported-by: kernel test robot <lkp@intel.com>
Reviewed-by: Bean Huo <beanhuo@micron.com>
Reviewed-by: Stanley Chu <stanley.chu@mediatek.com>
Co-developed-by: Asutosh Das <asutoshd@codeaurora.org>
Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
Signed-off-by: Can Guo <cang@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>