drm: pl111: Move VExpress setup into versatile init

Since the VExpress setup in pl111_vexpress.c is now just a single
function call, let's move it into pl111_versatile.c and we can further
simplify pl111_versatile_init() by moving the other pieces for VExpress
into pl111_vexpress_clcd_init().

Cc: Eric Anholt <eric@anholt.net>
Cc: dri-devel@lists.freedesktop.org
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200409013947.12667-4-robh@kernel.org