[llvm-readobj] Fix COFF RVA table dumping bug

We would return an error in getVaPtr if the RVA table being dumped was
the last data in the .rdata section. Avoid the issue by subtracting one
from the offset and adding it back to get an open interval again.

llvm-svn: 306171
diff --git a/llvm/test/tools/llvm-readobj/coff-load-config.test b/llvm/test/tools/llvm-readobj/coff-load-config.test
index 97bd2e0..1eb67be 100644
--- a/llvm/test/tools/llvm-readobj/coff-load-config.test
+++ b/llvm/test/tools/llvm-readobj/coff-load-config.test
@@ -1,6 +1,8 @@
 RUN: llvm-readobj -coff-load-config %S/Inputs/coff-load-config-x86.dll | FileCheck %s --check-prefix=X86
 RUN: llvm-readobj -coff-load-config %S/Inputs/coff-load-config-x64.dll | FileCheck %s --check-prefix=X64
 
+RUN: llvm-readobj -coff-load-config %S/Inputs/coff-load-config-data-end.exe | FileCheck %s --check-prefix=DATAEND
+
 X86: LoadConfig [
 X86:   Size: 0x5C
 X86:   TimeDateStamp: 1970-01-01 00:00:00 (0x0)
@@ -85,3 +87,7 @@
 X64:   0x180001B50
 X64:   0x180001D90
 X64: ]
+
+DATAEND: SEHTable [
+DATAEND-NEXT:   0x402006
+DATAEND-NEXT: ]