ARM64: configs: tegra18: disable nvmap stashing

ARM64: configs: tegra18: disable nvmap stashing

Now that dmabuf stashing is enabled, nvmap stashing does
not provide any other advantage. Also, stashing mappings
for host1x context devices is a security hole. Since, nvmap
stashed those mappings as well, it is undesirable. Dmabuf
stashing is disabled for such devices so issue is not seen
with dmabuf stashing alone.

no change in boot.img size

bug 200229632

Change-Id: I518d06d670deeee40661b99ed9ecb44c1d73c8f7
Signed-off-by: Sri Krishna chowdary <schowdary@nvidia.com>
Reviewed-on: http://git-master/r/1302905
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>