wdi: Get bEnableSSR back into WDI_ControlBlockType

The support for enabling and disabling SSR requires the bEnableSSR
member of the WDI_ControlBlockType, but this was most likely erroneously
removed in 9af07cf.

Signed-off-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>

Change-Id: Ie311b6877e8951ee9c6635081d43ddc642d9855b