drm/radeon: replace udelay with mdelay for long timeouts

Some architectures require that delays longer than a few
miliseconds are called through mdelay. This was triggered
on ARM randconfig builds.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/radeon/r600.c b/drivers/gpu/drm/radeon/r600.c
index 391bd26..de71243 100644
--- a/drivers/gpu/drm/radeon/r600.c
+++ b/drivers/gpu/drm/radeon/r600.c
@@ -2839,7 +2839,7 @@
 		/* r7xx asics need to soft reset RLC before halting */
 		WREG32(SRBM_SOFT_RESET, SOFT_RESET_RLC);
 		RREG32(SRBM_SOFT_RESET);
-		udelay(15000);
+		mdelay(15);
 		WREG32(SRBM_SOFT_RESET, 0);
 		RREG32(SRBM_SOFT_RESET);
 	}