ata: Disable AHCI ALPM feature for Ampere Computing eMAG SATA

Due to hardware errata, Ampere Computing eMAG SATA can't support
AHCI ALPM feature. This patch disables the AHCI ALPM feature for
eMAG SATA.

Signed-off-by: Suman Trpathi <stripathi@amperecomputing.com>
Signed-off-by: Rameshwar Prasad Sahu <rameshwar.sahu@amperecomputing.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>