Staging: rtl8192e: fix timeouts on firmware download

We need to actually wait a specific ammount of time, not just hope that
a set number of loops will be long enough.

Based on a conversation with Ralink, and a proposed patch for their
older kernel driver.

Cc: david woo <xinhua_wu@realsil.com.cn>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>