intel: 48b ppgtt support (EXEC_OBJECT_SUPPORTS_48B_ADDRESS flag)

Gen8+ supports 48-bit virtual addresses, but some objects must always be
allocated inside the 32-bit address range.

In specific, any resource used with flat/heapless (0x00000000-0xfffff000)
General State Heap (GSH) or Instruction State Heap (ISH) must be in a
32-bit range, because the General State Offset and Instruction State Offset
are limited to 32-bits.

The i915 driver has been modified to provide a flag to set when the 4GB
limit is not necessary in a given bo (EXEC_OBJECT_SUPPORTS_48B_ADDRESS).
48-bit range will only be used when explicitly requested.

Callers to the existing drm_intel_bo_emit_reloc function should set the
use_48b_address_range flag beforehand, in order to use full ppgtt range.

v2: Make set/clear functions nops on pre-gen8 platforms, and use them
    internally in emit_reloc functions (Ben)
    s/48BADDRESS/48B_ADDRESS/ (Dave)
v3: Keep set/clear functions internal, no-one needs to use them directly.
v4: Don't set 48bit-support flag in emit reloc, check for ppgtt type
    before enabling set/clear function, print full offsets in debug
    statements, using port of lower_32_bits and upper_32_bits from linux
    kernel (Michał)

References: http://lists.freedesktop.org/archives/intel-gfx/2015-July/072612.html


Cc: Ben Widawsky <ben@bwidawsk.net>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Signed-off-by: Michel Thierry <michel.thierry@intel.com>
Reviewed-by: Kristian Høgsberg Kristensen <kristian.h.kristensen@intel.com>
Signed-off-by: Kristian Høgsberg Kristensen <kristian.h.kristensen@intel.com>