drm: drop README.drm, ancient scrolls

This stuff is ancient, we have docs now in the kernel,
lets just drop it.

Pointed out by Glenn
Reviewed-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/README.drm

-************************************************************
-* For the very latest on DRI development, please see:      *
-*     http://dri.freedesktop.org/                          *
-************************************************************
-
-The Direct Rendering Manager (drm) is a device-independent kernel-level
-device driver that provides support for the XFree86 Direct Rendering
-Infrastructure (DRI).
-
-The DRM supports the Direct Rendering Infrastructure (DRI) in four major
-ways:
-
-    1. The DRM provides synchronized access to the graphics hardware via
-       the use of an optimized two-tiered lock.
-
-    2. The DRM enforces the DRI security policy for access to the graphics
-       hardware by only allowing authenticated X11 clients access to
-       restricted regions of memory.
-
-    3. The DRM provides a generic DMA engine, complete with multiple
-       queues and the ability to detect the need for an OpenGL context
-       switch.
-
-    4. The DRM is extensible via the use of small device-specific modules
-       that rely extensively on the API exported by the DRM module.
-
-
-Documentation on the DRI is available from:
-    http://dri.freedesktop.org/wiki/Documentation
-    http://sourceforge.net/project/showfiles.php?group_id=387
-    http://dri.sourceforge.net/doc/
-
-For specific information about kernel-level support, see:
-
-    The Direct Rendering Manager, Kernel Support for the Direct Rendering
-    Infrastructure
-    http://dri.sourceforge.net/doc/drm_low_level.html
-
-    Hardware Locking for the Direct Rendering Infrastructure
-    http://dri.sourceforge.net/doc/hardware_locking_low_level.html
-
-    A Security Analysis of the Direct Rendering Infrastructure
-    http://dri.sourceforge.net/doc/security_low_level.html