spi: altera: Zap endless loop

spi: altera: Zap endless loop

The driver contained an endless loop when waiting for TX completion,
this is a bad idea since if the hardware fails, the loop might spin
forever. Add timeout and handle it.

Signed-off-by: Marek Vasut <[email protected]>
Cc: Chin Liang See <[email protected]>
Cc: Dinh Nguyen <[email protected]>
Cc: Albert Aribaud <[email protected]>
Cc: Pavel Machek <[email protected]>
Cc: Jagannadha Sutradharudu Teki <[email protected]>
Acked-by: Pavel Machek <[email protected]>
Reviewed-by: Jagannadha Sutradharudu Teki <[email protected]>