sis190: scheduling while atomic error

sis190_tx_timeout
-> sis190_hw_start
   -> sis190_soft_reset
      -> msleep *splat*

PCI transactions are correctly flushed here.
The msleep() is probably useless.

Signed-off-by: Francois Romieu <romieu@fr.zoreil.com>
Cc: K.M. Liu <kmliu@sis.com.tw>