drm/radeon/kms: increase rom size for atrm method

The vbios rom is >64k on a lot of modern asics.  Increase
the fetch size for atrm to make sure we don't miss part
of a larger rom.
Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/radeon_bios.c

@@ -104,7 +104,7 @@ static bool radeon_read_bios(struct radeon_device *rdev)
 static bool radeon_atrm_get_bios(struct radeon_device *rdev)
 {
 	int ret;
-	int size = 64 * 1024;
+	int size = 256 * 1024;
 	int i;
 
 	if (!radeon_atrm_supported(rdev->pdev))