drm/msm: gpu: call qcom_mdt interfaces only for ARCH_QCOM

When compile-testing for something other than ARCH_QCOM,
we run into a link error:

drivers/gpu/drm/msm/adreno/a5xx_gpu.o: In function `a5xx_hw_init':
a5xx_gpu.c:(.text.a5xx_hw_init+0x600): undefined reference to `qcom_mdt_get_size'
a5xx_gpu.c:(.text.a5xx_hw_init+0x93c): undefined reference to `qcom_mdt_load'

There is already an #ifdef that tries to check for CONFIG_QCOM_MDT_LOADER,
but that symbol is only meaningful when building for ARCH_QCOM.

This adds a compile-time check for ARCH_QCOM, and clarifies the
Kconfig select statement so we don't even try it for other targets.

The check for CONFIG_QCOM_MDT_LOADER can then go away, which also
improves compile-time coverage and makes the code a little nicer
to read.

Fixes: 7c65817e6d38 ("drm/msm: gpu: Enable zap shader for A5XX")
Acked-by: Jordan Crouse <[e-mail]>
Acked-by: Bjorn Andersson <[e-mail]>
Signed-off-by: Arnd Bergmann <[e-mail]>
Signed-off-by: Rob Clark <[e-mail]>

drivers/gpu/drm/msm/Kconfig

···
 	depends on ARCH_QCOM || (ARM && COMPILE_TEST)
 	depends on OF && COMMON_CLK
 	depends on MMU
-	select QCOM_MDT_LOADER
+	select QCOM_MDT_LOADER if ARCH_QCOM
 	select REGULATOR
 	select DRM_KMS_HELPER
 	select DRM_PANEL

drivers/gpu/drm/msm/adreno/a5xx_gpu.c

···
 
 #define GPU_PAS_ID 13
 
-#if IS_ENABLED(CONFIG_QCOM_MDT_LOADER)
-
 static int zap_shader_load_mdt(struct device *dev, const char *fwname)
 {
 	const struct firmware *fw;
···
 	ssize_t mem_size;
 	void *mem_region = NULL;
 	int ret;
+
+	if (!IS_ENABLED(CONFIG_ARCH_QCOM))
+		return -EINVAL;
 
 	/* Request the MDT file for the firmware */
 	ret = request_firmware(&fw, fwname, dev);
···
 
 	return ret;
 }
-#else
-static int zap_shader_load_mdt(struct device *dev, const char *fwname)
-{
-	return -ENODEV;
-}
-#endif
 
 static void a5xx_submit(struct msm_gpu *gpu, struct msm_gem_submit *submit,
 	struct msm_file_private *ctx)