arm: tegra: remove generic disp clock divisor flag

Although disp1 and disp2 have 7.1 divisors, their corresponding
registers in the clk_rst block are not the interface to program the
divisors.  Setting the generic DIV_U71 flag may cause the code to
attempt to program the clock at a different divisor, which will confuse
any code attempting to use that clock since it isn't actually being
divided.

Signed-off-by: Robert Morell <rmorell@nvidia.com>
Signed-off-by: Colin Cross <ccross@android.com>