mmc: dw_mmc: fix warning reported by kernel-doc

mmc: dw_mmc: fix warning reported by kernel-doc

Try to fix the warning reported by:
scripts/kernel-doc -man -v include/linux/mmc/dw_mmc.h > /dev/null

warning: No description found for parameter 'irq_lock'
warning: No description found for parameter 'stop_abort'
warning: No description found for parameter 'prev_blksz'
warning: No description found for parameter 'timing'
warning: No description found for parameter 'ring_size'
warning: No description found for parameter 'dms'
warning: No description found for parameter 'phy_regs'
warning: No description found for parameter 'fifoth_val'
warning: No description found for parameter 'vqmmc_enabled'
warning: No description found for parameter 'cmd11_timer'
warning: Excess struct/union/enum/typedef member 'card_tasklet'
description in 'dw_mci'

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>