broadwell: Fix serial IO DMA controller interrupt

SDMA uses INTB/IRQ6 instead of INTC/IRQ7.

BUG=chrome-os-partner:37548
BRANCH=broadwell
TEST=emerge-samus coreboot

Change-Id: I134ab659fc35790a29382da1c269cf6271f3d8eb
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/262527
Reviewed-by: Sameer Nanda <snanda@chromium.org>
Reviewed-by: Ben Zhang <benzh@google.com>
Tested-by: Ben Zhang <benzh@google.com>
(cherry picked from commit 736904332926bf981f1ce39fb45e005aa20ede06)
Reviewed-on: https://chromium-review.googlesource.com/263279
1 file changed