shader_checker: Check for duplicate VI binding descriptions.

Signed-off-by: Chris Forbes <chrisf@ijw.co.nz>
Reviewed-by: Tobin Ehlis <tobin@lunarg.com>
diff --git a/layers/shader_checker.h b/layers/shader_checker.h
index 17692fb..4ec8dea 100644
--- a/layers/shader_checker.h
+++ b/layers/shader_checker.h
@@ -35,4 +35,5 @@
     SHADER_CHECKER_NON_SPIRV_SHADER,        /* Shader image is not SPIR-V */
     SHADER_CHECKER_INCONSISTENT_SPIRV,      /* General inconsistency within a SPIR-V module */
     SHADER_CHECKER_UNKNOWN_STAGE,           /* Stage is not supported by analysis */
+    SHADER_CHECKER_INCONSISTENT_VI,         /* VI state contains conflicting binding or attrib descriptions */
 } SHADER_CHECKER_ERROR;