[ALPS05470078] mmc: fix mmc_data null pointer when msdc request timeout

[Detail]
When msdc request timeout, because no concurrency protection, the
mmc_data in host maybe set to null, then OOPS when get the mmc command
at the beginning of msdc_data_xfer_done.

[Solution]
Getting the mmc command after double checking host state.

MTK-Commit-Id: 204c87339f47a815939b6926b0635a71e186c54a

Change-Id: Ie7d24f4be6937872304e26cbd264cb4560965f95
CR-Id: ALPS05470078
Feature: eMMC
Signed-off-by: Yanghui Li <yanghui.li@mediatek.com>