drm/eld: replace uint8_t with u8

Unify on kernel types.

Cc: Mitul Golani <mitulkumar.ajitkumar.golani@intel.com>
Reviewed-by: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>
Reviewed-by: Mitul Golani <mitulkumar.ajitkumar.golani@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/6e048fc4c8a3ebec638ce27b0b8b969a3d2fa8bc.1698747331.git.jani.nikula@intel.com