Write and read back mode register to check that a chip is really there.
If no card is present, reads result in 0xff.
Signed-off-by: NOndrej Zary <linux@rainbow-software.org>
Signed-off-by: NFinn Thain <fthain@telegraphics.com.au>
Tested-by: NOndrej Zary <linux@rainbow-software.org>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>