ARM: OMAP4+: dpll: remove cpu_is_omap44xx checks

These are unnecessary, as the clock code is only used on OMAP4+ platforms
through clock registrations. This also allows to eventually migrate the
clock type implementation under clock driver.

Signed-off-by: Tero Kristo <t-kristo@ti.com>
Reviewed-by: Mike Turquette <mturquette@linaro.org>
Signed-off-by: Paul Walmsley <paul@pwsan.com>