MIPS: Netlogic: Fix cop0 prid check in AHCI init

PRID register should be masked with IMP_MASK to get processor ID.

Signed-off-by: Ganesan Ramalingam <ganesanr@broadcom.com>
Signed-off-by: Jayachandran C <jchandra@broadcom.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/8883/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>