mmc: core: Add MMC Command Queue Support kernel parameter

This parameter offers a workaround for cards that report command queue
(CMDQ) support but don't work correctly when CMDQ is enabled. At least
some ROCKPro64 + Foresee (32GB) eMMC card combinations have trouble
working correctly. Setting mmc_cmdqueue=off in kernel command line
disables CMDQ support and may help with troublesome hardware.