IB/ehca: Activate scaling code by default

Change ehca's Kconfig to activates scaling code as default. After
several measurements we saw that this feature prevents dropped packets
(UD) in stress situation. Thus, enabling it helps to improve ehca's
bandwidth through IPoIB.

Signed-off-by: Hoang-Nam Nguyen <[e-mail]>
Signed-off-by: Roland Dreier <[e-mail]>

drivers/infiniband/hw/ehca/Kconfig

···
 config INFINIBAND_EHCA_SCALING
 	bool "Scaling support (EXPERIMENTAL)"
 	depends on IBMEBUS && INFINIBAND_EHCA && HOTPLUG_CPU && EXPERIMENTAL
+	default y
 	---help---
 	eHCA scaling support schedules the CQ callbacks to different CPUs.