disk: Fix usdhc driver out-of-bounds array access
disk: Fix usdhc driver out-of-bounds array access

The usdhc driver was incorrectly post-decrementing a do/while loop
iterator, causing an extra iteration of the loop and an out-of-bounds
array access. Change the iterator to decrement within the loop instead.

Tested samples/subsys/fs/fat_fs on the mimxrt1050_evk board.

Coverity-CID: 203403

Signed-off-by: Maureen Helm <87a696db5547fa477bda9f9e0f00013c839c14d3@nxp.com>

zephyrproject-rtos/zephyr,Vudentz/zephyr,finikorg/zephyr,nashif/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,nashif/zephyr,finikorg/zephyr,nashif/zephyr,Vudentz/zephyr,Vudentz/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,galak/zephyr,nashif/zephyr