mmc: core: implement enhanced strobe support

Controllers use data strobe line to latch data from devices
under hs400 mode, but not for cmd line. So since emmc 5.1, JEDEC
introduces enhanced strobe mode for latching cmd response from
emmc devices to host controllers. This new feature is optional,
so it depends both on device's cap and host's cap to decide
whether to use it or not.

Change-Id: I1ca2bff37ae697f5c502975d1dc54d534151a3cd
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
Tested-by: Douglas Anderson <dianders@chromium.org>
Tested-by: Jaehoon Chung <jh80.chung@samsung.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Git-commit: 81ac2af65793ecfbd79875d45043ff4adc0982b8
Git-repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git


[vviswana@codeaurora.org: Adjusted patch for internal driver]
Signed-off-by: Vijay Viswanath <vviswana@codeaurora.org>