floppy: Send 4 sense interrupt commands during controller initialization

floppy: Send 4 sense interrupt commands during controller initialization

During initialization, real floppy controllers need 4 sense interrupt commands
to clear the interrupt status (this represents the transition from "not ready"
to "ready" for each of the four virtual floppy drives), instead of just one.

This is described in detail in section 7.4 - Drive Polling of the Intel 82077AA
datasheet.

Signed-off-by: Nikolay Nikolov <nickysn@users.sourceforge.net>