ARM: i.MX6: clk: add i.MX6 DualLite differences

The CCM_CBCMR register (address 0x02C4018) has different meaning
between the i.MX6 Quad/Dual and the i.MX6 Solo/DualLite.

Compared to the i.MX6 Quad/Dual, the CCM_CBCMR register in the
i.MX6 Solo/DualLite doesn't have a gpu3d_shader configuration and
moves the gpu2_core configuration at that place.

Handle these i.MX6 Quad/Dual vs. i.MX6 Solo/DualLite clock differences
by using cpu_is_mx6dl().

Signed-off-by: Dirk Behme <dirk.behme@de.bosch.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>