drm/tegra: Changes for v4.1-rc1

Perhaps the most noteworthy change in this set is the implementation of
a hardware VBLANK counter using host1x syncpoints. The SOR registers can
now be dumped via debugfs, which can be useful while debugging. The IOVA
address space maintained by the driver can also be dumped via debugfs.

Other than than, these changes are mostly cleanup work, such as making
register names more consistent or removing unused code (that was left
over after the atomic mode-setting conversion). There's also a fix for
eDP that makes the driver cope with firmware that already initialized
the display (such as the firmware on the Tegra-based Chromebooks).

* tag 'drm/tegra/for-4.1-rc1' of git://anongit.freedesktop.org/tegra/linux:
  drm/tegra: sor: Reset during initialization
  drm/tegra: gem: Return 64-bit offset for mmap(2)
  drm/tegra: hdmi: Name register fields consistently
  drm/tegra: hdmi: Resets are synchronous
  drm/tegra: dc: Document tegra_dc_state_setup_clock()
  drm/tegra: dc: Remove unused callbacks
  drm/tegra: dc: Remove unused function
  drm/tegra: dc: Use base atomic state helpers
  drm/atomic: Add helpers for state-subclassing drivers
  drm/tegra: dc: Implement hardware VBLANK counter
  gpu: host1x: Export host1x_syncpt_read()
  drm/tegra: sor: Dump registers via debugfs
  drm/tegra: sor: Registers are 32-bit
  drm/tegra: Provide debugfs file for the IOVA space
  drm/tegra: dc: Check for valid parent clock