vc4: Set shareable BOs as T tiled if possible

vc4: Set shareable BOs as T tiled if possible

X11 and GL compositor performance on VC4 has been terrible because of our
SHARED-usage buffers all being forced to linear.  This swaps SHARED &&
!LINEAR buffers over to being tiled.

This is an expected win for all GL compositors during rendering (a full
copy of each shared texture per draw call), allows X11 to be used with
decent performance without a GL compositor, and improves X11 windowed
swapbuffers performance as well.  It also halves the memory usage of
shared buffers that get textured from.  The only cost should be idle
systems with a scanout-only buffer that isn't flagged as LINEAR, in which
case the memory bandwidth cost of scanout goes up ~25%.

This implements the EGL_EXT_image_dma_buf_import_modifiers extension,
supporting the VC4 T_TILED modifier.

v2: Added modifier support to resource creation/import, and
    advertisement (by daniels).
v3: Fix old-kernel fallback path, fix compiler error and warnings, and
    comment touchups (by anholt).

Reviewed-by: Daniel Stone <daniels@collabora.com>