tifm_sd: restructure initialization, removal and command handling

tifm_sd: restructure initialization, removal and command handling

In order to support correct suspend and resume several changes were needed:
1. Switch from work_struct to tasklet for command handling. When device
suspend is called workqueues are already frozen and can not be used.
2. Separate host initialization code from driver's probe and don't rely
on interrupts for host initialization. This, in turn, addresses two
problems:
 a) Resume needs to re-initialize the host, but can not assume that
    device interrupts were already re-armed.
 b) Previously, probe will return successfully before really knowing
    the state of the host, as host interrupts were not armed in time.
    Now it uses polling to determine the real host state before returning.
3. Separate termination code from driver's remove. Termination may be caused
by resume, if media changed type or became unavailable during suspend.

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