Remove default value from spi_bb_i constructor

We dont want to provide magic predefine settings to the user. If the user
code needs default contructor, then the derived class can have one.

include/utl/com/spi_bb.h

@@ -66,7 +66,7 @@ namespace utl {
    protected:
       ~spi_bb_i () = default; //!< A default destructor, allow destructor from derived only
       //! \brief A default constructor
-      spi_bb_i (uint32_t clk =1000000) noexcept
+      spi_bb_i (uint32_t clk) noexcept
          : nsec_ {1000000000/(2*clk)} {
       }
    //!@}
@@ -198,7 +198,7 @@ namespace utl {
    protected:
       ~spi_bb_i () = default; //!< A default destructor, allow destructor from derived only
       //! \brief A default constructor
-      spi_bb_i (uint32_t clk =1000000) noexcept
+      spi_bb_i (uint32_t clk) noexcept
          : nsec_ {1000000000/(2*clk)} {
       }
    //!@}