tifm_sd: replace command completion state machine with full checking

State machine used to to track mmc command state was found to be fragile
and unreliable, making many cards unusable. The safer solution is to perform
all needed checks at every card event.

Signed-off-by: Alex Dubov <oakad@yahoo.com>
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>