ARM: dts: msm: Reduce WCNSS carveout to 5MB for msm8909 1GB devices

WCNSS image size has been optimized for 1GB
devices and now needs only 5MB carveout instead of
6MB. Previously we had seperated peripheral_mem
node for 512MB devices as there was difference in
size of WCNSS image for 1GB and 512MB target.
Continue maintaining different node for 1GB and
512MB target to meet any future change in image size.

Change-Id: I5d09980351df30e2ef4dc419125d5767cf7255d2
Signed-off-by: Susheel Khiani <skhiani@codeaurora.org>