drm/i915/dmc: Rename macro names containing csr

Rename all occurences of CSR_* with DMC_*

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Signed-off-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210518213444.11420-4-anusha.srivatsa@intel.com