drm/xe: Fix unmet direct dependencies warning

WARNING: unmet direct dependencies detected for FB_IOMEM_HELPERS
  Depends on [n]: HAS_IOMEM [=y] && FB_CORE [=n]
  Selected by [m]:
  - DRM_XE_DISPLAY [=y] && HAS_IOMEM [=y] && DRM [=m] && DRM_XE [=m] && DRM_XE [=m]=m [=m] && HAS_IOPORT [=y]

DRM_XE_DISPLAY requires FB_IOMEM_HELPERS, but the dependency FB_CORE is
missing, selecting FB_IOMEM_HELPERS if DRM_FBDEV_EMULATION is set as
other drm drivers.

Fixes: 44e6949 ("drm/xe/display: Implement display support")
Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250323114103.1960511-1-yuehaibing@huawei.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

drivers/gpu/drm/xe/Kconfig

@@ -53,7 +53,7 @@ config DRM_XE
 config DRM_XE_DISPLAY
 	bool "Enable display support"
 	depends on DRM_XE && DRM_XE=m && HAS_IOPORT
-	select FB_IOMEM_HELPERS
+	select FB_IOMEM_HELPERS if DRM_FBDEV_EMULATION
 	select I2C
 	select I2C_ALGOBIT
 	default y