mmc: rtsx: modify error handle and remove smatch warnings

mmc: rtsx: modify error handle and remove smatch warnings

Using non-DMA dump-regs, which would be more exactly for DMA transfer
failed.  More careful handling when cmd/data timeout, add stop(CMD12)
cmd before go to finish request when multi-rw timeout.

Remove some static checker warings.
on commit: <mmc: rtsx: add support for pre_req and post_req>

drivers/mmc/host/rtsx_pci_sdmmc.c:194 sd_finish_request()
error: we previously assumed 'mrq' could be null (see line 158)
drivers/mmc/host/rtsx_pci_sdmmc.c:504 sd_get_rsp()
error: we previously assumed 'cmd' could be null (see line 434)
drivers/mmc/host/rtsx_pci_sdmmc.c:525 sd_pre_dma_transfer()
warn: we tested 'next' before and it was 'false'

Signed-off-by: Micky Ching <micky_ching@realsil.com.cn>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Chris Ball <chris@printf.net>