[spirv][ir] Add  some missing decorations.

This CL adds the `coherent` annotation to variables and function
parameters where needed. The `NonWritable` and `NonReadable` annotations
are also added to function parameters.

Change-Id: I93fdffa2c40f8bcccfa50b744ad30880d1d1e2b5
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/203294
Reviewed-by: James Price <jrprice@google.com>
Commit-Queue: dan sinclair <dsinclair@chromium.org>
diff --git a/test/tint/builtins/gen/var/subgroupBroadcast/279027.wgsl.expected.spvasm b/test/tint/builtins/gen/var/subgroupBroadcast/279027.wgsl.expected.spvasm
index 0a9c96b..393da3d 100644
--- a/test/tint/builtins/gen/var/subgroupBroadcast/279027.wgsl.expected.spvasm
+++ b/test/tint/builtins/gen/var/subgroupBroadcast/279027.wgsl.expected.spvasm
@@ -21,6 +21,7 @@
                OpDecorate %tint_symbol_1 Block
                OpDecorate %1 DescriptorSet 0
                OpDecorate %1 Binding 0
+               OpDecorate %1 Coherent
        %uint = OpTypeInt 32 0
      %v4uint = OpTypeVector %uint 4
 %tint_symbol_1 = OpTypeStruct %v4uint