Clock Control.
| INTERNAL_CLK_EN | Internal Clock Enable. |
| INTERNAL_CLK_STABLE | Internal Clock Stable. |
| SD_CLK_EN | SD Clock Enable. |
| CLK_GEN_SEL | Clock Generator Select. |
| UPPER_SDCLK_FREQ_SEL | Upper Bits of SDCLK Frequency Select. |
| SDCLK_FREQ_SEL | SDCLK Frequency Select. |