mfd: sec: Remove PMICs without compatibles

The S5M8751 and S5M8763 PMIC chips have no corresponding compatible
values, so since board file support was removed for this driver, there
is no way to specify these PMICs as present in boards anymore.
Remove leftovers of these chips since it's dead code.

Signed-off-by: David Virag <virag.david003@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20230131183008.4451-2-virag.david003@gmail.com