use new sdbus++ camelcase for CSR.

Change I17a8d7479556596a3cf252b3f4eae9c8df547189 will change
how sdbus++ generates names which start with an acronym.
Prepare for this by keying off the SDBUSPP_NEW_CAMELCASE
define to use the new format.

Changes:
    cSR() -> csr()

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I9adb628d7d064af9f65d37aebe99e06532690163
diff --git a/csr.hpp b/csr.hpp
index 728cfef..45ebf00 100644
--- a/csr.hpp
+++ b/csr.hpp
@@ -39,7 +39,11 @@
         CertInstallPath&& installPath, const Status& status);
     /** @brief Return CSR
      */
+#ifdef SDBUSPP_NEW_CAMELCASE
+    std::string csr() override;
+#else
     std::string cSR() override;
+#endif
 
   private:
     /** @brief sdbusplus handler */