sata_fsl: Fix wrong Device Error Register usage

sata_fsl: Fix wrong Device Error Register usage

When a single device error is detected, the device under the error
is indicated by the error bit set in the DER. There is a one to one
mapping between register bit and devices on Port multiplier(PMP)
i.e. bit 0 represents PMP device 0 and bit 1 represents PMP device
1 etc.

Current implementation treats Device error register value as device
number not set of bits representing multiple device on PMP. It is
changed to consider bit level.

No need to check for each set bit as all command is going to be
aborted.

Signed-off-by: Ashish Kalra <B00888@freescale.com>
Signed-off-by: Prabhakar Kushwaha <prabhakar@freescale.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>