drm/pl111: Actually fix CONFIG_VEXPRESS_CONFIG depends

VEXPRESS_CONFIG needs to either be missing, built-in, or modular when
pl111 is modular. Update the Kconfig to reflect the need.

Fixes: 4dc7c97d ("drm/pl111: depend on CONFIG_VEXPRESS_CONFIG")
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210604014055.4060521-1-keescook@chromium.org

drivers/gpu/drm/pl111/Kconfig

@@ -2,7 +2,8 @@
 config DRM_PL111
 	tristate "DRM Support for PL111 CLCD Controller"
 	depends on DRM
-	depends on VEXPRESS_CONFIG
+	depends on ARM || ARM64 || COMPILE_TEST
+	depends on VEXPRESS_CONFIG || VEXPRESS_CONFIG=n
 	depends on COMMON_CLK
 	select DRM_KMS_HELPER
 	select DRM_KMS_CMA_HELPER