Fix section relocation for SECTIONREL32 with immediate offset.

Patch by Kai Nacke. This matches the gnu as output.

llvm-svn: 180568
diff --git a/llvm/lib/MC/MCExpr.cpp b/llvm/lib/MC/MCExpr.cpp
index d54c264..6cde26c 100644
--- a/llvm/lib/MC/MCExpr.cpp
+++ b/llvm/lib/MC/MCExpr.cpp
@@ -288,6 +288,8 @@
     .Case("tlvp", VK_TLVP)
     .Case("IMGREL", VK_COFF_IMGREL32)
     .Case("imgrel", VK_COFF_IMGREL32)
+    .Case("SECREL32", VK_SECREL)
+    .Case("secrel32", VK_SECREL)
     .Default(VK_Invalid);
 }