mmc: core: Fix issues observed with DRV_IN/OUT requests handling

With newly added DRV IN/OUT type of request handling in command queue
<607fdf34> ("MMC: Core: Fix reading ext_csd and status from debugfs")
device hang upon reboot issues are reported.
Host lock was not getting released after handling the DRV IN/OUT
requests. This is blocking other processes to complete their disk
requests, which is eventually leading to hang.

Now host lock is released after processing DRV IN/OUT type of requests.

Change-Id: I94b7925cc1207f3adb46428edf6088bab6356835
Signed-off-by: Ram Prakash Gupta <rampraka@codeaurora.org>