drm/amdgpu: fix eGPU hotplug regression

The driver needs to wait for the on board firmware
to finish its initialization before probing the card.
Commit 95905698 ("drm/amdgpu: Fix discovery initialization failure during pci rescan")
switched from using msleep() to using usleep_range() which
seems to have caused init failures on some navi1x boards. Switch
back to msleep().

Fixes: 95905698 ("drm/amdgpu: Fix discovery initialization failure during pci rescan")
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/3559
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/3500Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: Ma Jun <Jun.Ma2@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c

@@ -278,7 +278,7 @@ static int amdgpu_discovery_read_binary_from_mem(struct amdgpu_device *adev,
 			msg = RREG32(mmMP0_SMN_C2PMSG_33);
 			if (msg & 0x80000000)
 				break;
-			usleep_range(1000, 1100);
+			msleep(1);
 		}
 	}