[intel-i915] Support training aux read interval

Test: Complete link training with previously failing displays
Change-Id: I76aec7e6691a0a05f40f53e699ca42edaccd03fa

[intel-i915] Allow DP to handle hotplug events

Change-Id: I91d123cfafe7a6e8f920f61f899e20afb82fd3c9

[intel-i915] Improve DP link configuration

- Select the fastest DP link rate
- Don't use 4 lanes on DDI A if they're not available

Change-Id: Ied32b850d54d9838ccdd4da1d579d907dc01b987

[intel-i915] Reinitialize displays on resume

Change-Id: I22449d4896d331c4808a9341ab5ea325a45a7472

[intel-i915] Add panel power and backlight control

Change-Id: I92682eed0bdcfd8687d89a56f1fa2a597e4b01be

[ulib][hwreg] Add support for fluent setting

This was a requested feature for reducing visual clutter on
registers that have many fields to set.

Change-Id: I91cb550f841f08499e8900285d2375514691feb2

[dev][i915] Switch code over to hwreg lib

The hwreg code is derived from registers-base.h and has support for
additional features (like reserved-zero bits).

Change-Id: I1476a23de273896e029c99231833d30d4105e3cd

[system][intel-i915] Add DisplayPort configuration

Change-Id: I7ff60fa0be08f8ebbed048829c677aec7fa69c3e