CLK: TI: always enable DESHDCP clock

DESHDCP clock is needed on DRA7 based SoCs to enable the DSS IP. That
clock is an odd one, as it is not supposed to be any kind of core clock
for DSS, and we don't even support HDCP, but the clock is still needed
even for the HWMOD framework to be able to reset the DSS IP.

As there's no support for multiple core clocks in the HWMOD framework,
we don't have any obvious place to enable this clock when DSS IP is
being enabled.

Furthermore, the HDMI on OMAP5 DSS is the same as on DRA7, and OMAP5
does not have any such clock configuration bit. This suggests that on
OMAP5 the DESHDCP clock is always enabled, and for DRA7 we have the
possibility to gate it.

So, as we don't have any clean way to enable and disable the clock
based on the need, this patch enables the clock at boot time, making it
work similarly to OMAP5.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Acked-by: Tero Kristo <t-kristo@ti.com>
Acked-by: Michael Turquette <mturquette@linaro.org>