egl/dri2: Put platform func names into proper namespaces

egl/dri2: Put platform func names into proper namespaces

Each of the egl_dri2 platforms (except Android) prefix their function
names with "dri2", not "dri2_${platform}". This means many function
names have three separate definitions in the egl_dri2 directory: one in
each of platform_drm.c, platform_wayland.c, and platform_x11.c. For
example, each of the three files defines dri2_create_window_surface().

The name collisions make it difficult to review patches for correctness
("Is this patch hunk calling a platform_x11 function or a global
egl_dri2 function?"), complicate debugging, and confuse code navigation
tools.

For each function in platform_x11.c prefixed with 'dri2', this patch
changes its prefix to 'dri2_x11'. Likewise for platform_drm.c and
'dri2_drm'; and platform_wayland.c and 'dri2_wl'.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Signed-off-by: Chad Versace <chad.versace@linux.intel.com>