[PULL REQ][Trusty SRU] Updates for X-Gene platforms

[Dann Frazier]

This branch includes a backported gpio driver and a couple of SATA
fixes for the X-Gene platform.
One of the SATA fixes is a revert of a patch that came in via upstream
stable that causes a regression for xgene-ahci. See commit logs and
referenced BugLinks for full details.

git://kernel.ubuntu.com/dannf/trusty-xgene.git for-ubuntu-20140629

Change Summary
=============
LP: #1334823:
70a09a36 UBUNTU: [Config] CONFIG_GPIO_DWAPB=m
d1dfa16 UBUNTU: SAUCE: (no-up) arm64: dts: Add Designware GPIO dts
binding to APM X-Gene platform
95ab481 gpio: dwapb: use a second irq chip
2e55022 gpio: dwapb: drop irq_setup_generic_chip()
b0f208a gpio: add a driver for the Synopsys DesignWare APB GPIO block

LP: #1335636:
950863d UBUNTU: SAUCE: (no-up) phy-xgene: Use correct tuning for Mustang

LP: #1335645:
e411219 Revert "libata/ahci: accommodate tag ordered controllers"