mmc: queue: exclude asynchronous transfer for special request
mmc: queue: exclude asynchronous transfer for special request

Unlike normal r/w request, special requests(discard, flush)
is finished with a one-time issue_fn. Request change to
mqrq_prev makes unnecessary call.

Signed-off-by: Seungwon Jeon <a133bc924ee401eac4c4f97927180f14b8a9baec@samsung.com>
Reviewed-by: Konstantin Dorfman <46030c539c9cb0a59b48c5bb1e425c3ab4b6c1d6@codeaurora.org>
Signed-off-by: Chris Ball <6ca7faee6ca9a094b1ee341f11b840a5608a8746@laptop.org>

TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs