mmc: core: Further fix thread wake-up

Commit e0097cf5 ("mmc: queue: Fix queue thread wake-up") did not go far
enough. mmc_wait_for_data_req_done() still contains some problems and can
be further simplified.  First it should not touch
context_info->is_waiting_last_req because that is a wake-up control used by
the owner of the context. Secondly, it should always return when one of its
wake-up conditions is met because, again, that is contolled by the owner of
the context.

While the current block driver does not have an issue, these problems were
exposed during testing of the Software Command Queue patches.

Fixes: e0097cf5 ("mmc: queue: Fix queue thread wake-up")
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Tested-by: Harjani Ritesh <riteshh@codeaurora.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>