Make type of register value in CHeaderGenerator configurable

[C-Elegans]

When generating a header file using the CHeaderGenerator, if you try to specify an alternative regType (such as uint32_t), the header it generated would include the following:

/**
  * @union       ap_config_reg_t
  * @address     0x0100
  * @brief       Configuration Register
  */
typedef union {
    u32 val;
    struct {
        uint32_t func_en   :  1; //RW, reset: 0x1, Function enable
        uint32_t reserved_0 : 31; //NA, Reserved
    } reg;
} ap_config_reg_t;

The members of the union would have their type set correctly, but the non-union member of the struct would not.

This PR changes it to generate the following:

/**
  * @union       ap_config_reg_t
  * @address     0x0100
  * @brief       Configuration Register
  */
typedef union {
    uint32_t val;
    struct {
        uint32_t func_en   :  1; //RW, reset: 0x1, Function enable
        uint32_t reserved_0 : 31; //NA, Reserved
    } reg;
} ap_config_reg_t;

[andreasWallner]

Thanks!