drm/atmel-hlcdc: Allow build with COMPILE_TEST=y

Allow atmel-hlcdc to be built with COMPILE_TEST=y for greater
coverage. Builds fine on x86/x86_64 at least.

Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Boris Brezillon <bbrezillon@kernel.org>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240408170426.9285-17-ville.syrjala@linux.intel.comAcked-by: Sam Ravnborg <sam@ravnborg.org>

drivers/gpu/drm/atmel-hlcdc/Kconfig

 # SPDX-License-Identifier: GPL-2.0-only
 config DRM_ATMEL_HLCDC
 	tristate "DRM Support for ATMEL HLCDC Display Controller"
-	depends on DRM && OF && COMMON_CLK && MFD_ATMEL_HLCDC && ARM
+	depends on DRM && OF && COMMON_CLK && ((MFD_ATMEL_HLCDC && ARM) || COMPILE_TEST)
 	select DRM_GEM_DMA_HELPER
 	select DRM_KMS_HELPER
 	select DRM_PANEL