[PATVH v3 0/3]mmc: set a suitable max_discard_sectors value for HC

[Chuanxiao Dong <chuanxiao.dong@intel.com>]

Hi,
	This is the version 3 patch which set a suitable max_discard_sectors
	value for SDHCI host controller. In this patch, a new quirk is added for
	such controller.

	max_discard_sectors is a parameter of MMC driver request queue. This
	value can limit how many sectors will be passed down to host for
	erasing. The original value for this parameter is UINT_MAX which means
	there is no limitation for the count of sectors to pass down for
	erasing.

	But some SDHCI host controller cannot erase too many sectors at one
	time. It may generate a timeout interrupt since the time erasing used is
	longer than the timeout time host can wait.

	So these patches add a new quirk for such SDHCI host controller and let
	it erase only signle eraseblock each time. This will be safe for such
	SDHCI host to use.

	patch1: add a new quirk for SDHCI host controller. Also add a new
	routine mmc_set_discard_limit which is used to set max_discard_sectors
	value for such SDHCI host controller.
	patch2: set timeout control register for such SDHCI host controller.
	patch3: add this quirk for MFLD SDHCI host controller.

	Change-log:
	patch1: let mmc_set_discard_limit can return value UINT_MAX.
	patch2: no change.
	patch3: no change.

Thanks
Chuanxiao