ARM: dts: msm: Reduce WCNSS carveout to 5MB for msm8909 512MB devices

WCNSS image size has been optimized for 512MB
devices and now needs only 5MB carveout instead of
6MB as previously required.

Change-Id: I10f8fcdb6f8e84a4bf67254891b34dc2a80116e3
Signed-off-by: Susheel Khiani <skhiani@codeaurora.org>