NVMeSensorMain: Fix clang-tidy bugprone-narrowing-conversion issue

clang-tidy-11 -p=build-clang ../src/NVMeSensorMain.cpp
../src/NVMeSensorMain.cpp:104:31: error: narrowing conversion from 'unsigned int' to signed type 'int' is implementation-defined [bugprone-narrowing-conversions,-warnings-as-errors]
                int rootBus = busNumber;
                              ^

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: I7e8312368a2b41924b2092d9324d515c6c2c81c8
diff --git a/src/NVMeSensorMain.cpp b/src/NVMeSensorMain.cpp
index 6c10eb5..7348733 100644
--- a/src/NVMeSensorMain.cpp
+++ b/src/NVMeSensorMain.cpp
@@ -80,8 +80,8 @@
                     continue;
                 }
 
-                unsigned int busNumber =
-                    std::visit(VariantToUnsignedIntVisitor(), findBus->second);
+                int busNumber =
+                    std::visit(VariantToIntVisitor(), findBus->second);
 
                 auto findSensorName = baseConfiguration->second.find("Name");
                 if (findSensorName == baseConfiguration->second.end())