spi: omap3: Fix timeout handling

spi: omap3: Fix timeout handling

The timeout value is never reset during the transfer. This means that when
transferring more data we eventually trigger the timeout.

This was reported on the mailing list:
"Spansion SPI flash read timeout with AM335x"

Signed-off-by: David Dueck <[email protected]>
CC: Tom Rini <[email protected]>
CC: Stefan Roese <[email protected]>
CC: Andy Pont <[email protected]>
Tested-by: David Dueck <[email protected]>
Reviewed-by: Jagannadha Sutradharudu Teki <[email protected]>