tools: io: add read method

Add method for reading the host's memory to enable reading the PCI
configuration.

Tested: Verified it's able to read a memory BAR associated with the
ASPEED ast2400.

Change-Id: Id06f30b063e69825f2dfa69786b69392657f7b1c
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/test/io_mock.hpp b/test/io_mock.hpp
index 2cff9a8..4d18204 100644
--- a/test/io_mock.hpp
+++ b/test/io_mock.hpp
@@ -12,6 +12,8 @@
   public:
     ~HostIoInterfaceMock() = default;
 
+    MOCK_METHOD3(read, bool(const std::size_t, const std::size_t, void* const));
+
     MOCK_METHOD3(write,
                  bool(const std::size_t, const std::size_t, const void* const));
 };