sysfs/sysfsread: add missing explicit to constructor

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: Id52936cb29563932dbd6e4cc52f4574e880e1f19
diff --git a/sysfs/sysfsread.hpp b/sysfs/sysfsread.hpp
index 349caac..4c1baec 100644
--- a/sysfs/sysfsread.hpp
+++ b/sysfs/sysfsread.hpp
@@ -12,7 +12,8 @@
 class SysFsRead : public ReadInterface
 {
   public:
-    SysFsRead(const std::string& path) : ReadInterface(), _path(FixupPath(path))
+    explicit SysFsRead(const std::string& path) :
+        ReadInterface(), _path(FixupPath(path))
     {}
 
     ReadReturn read(void) override;