ARM: OMAP2+: dpll: Add missing soc_is_am33xx() check for common functions

Add missing soc_is_am33xx() check for DPLL common control & clock
related functions, without this dpll programmability would be broken
for am33xx family of devices.

Signed-off-by: Vaibhav Hiremath <hvaibhav@ti.com>
Cc: Rajendra Nayak <rnayak@ti.com>
Cc: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>