drm/ast: Initialize DRAM type before posting GPU

Posting the GPU requires the correct DRAM type to be stored in
struct ast_private. Therefore first initialize the DRAM info and
then post the GPU. This restores the original order of instructions
in this function.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Fixes: bad09da6 ("drm/ast: Fixed vram size incorrect issue on POWER")
Cc: Joel Stanley <joel@jms.id.au>
Cc: Y.C. Chen <yc_chen@aspeedtech.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Emil Velikov <emil.l.velikov@gmail.com>
Cc: "Y.C. Chen" <yc_chen@aspeedtech.com>
Cc: <stable@vger.kernel.org> # v4.11+
Link: https://patchwork.freedesktop.org/patch/msgid/20200716125353.31512-6-tzimmermann@suse.de