Mips: loongson3_defconfig: Enable ast drm driver by default

ASpeed GPU is typically found on the Loongson server platform, as a
peripheral device driver, it generally should be compiled as a module.

Tested on loongson 3B4000 server[1].

[1] https://github.com/loongson-gfx/loongson_boards/tree/main/ls3b4000x2_server

Signed-off-by: Sui Jingfeng <suijingfeng@loongson.cn>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

Author: Sui Jingfeng

arch/mips/configs/loongson3_defconfig

@@ -283,6 +283,7 @@ CONFIG_DRM_AMDGPU_USERPTR=y
 CONFIG_DRM_AMD_ACP=y
 CONFIG_DRM_AMD_DC=y
 CONFIG_DRM_AMD_DC_SI=y
+CONFIG_DRM_AST=m
 CONFIG_DRM_RADEON=m
 CONFIG_DRM_QXL=y
 CONFIG_DRM_VIRTIO_GPU=y