ARM: AM33XX: clock: Add debugSS clock nodes

Represent debugSS clock interface as provided in
CM_WKUP_DEBUGSS_CLKCTRL register, includes
	- Clock gate for optional DEBUG_CLKA and DBGSYSCLK
	- Clock Mux for TRC_PMD and STM_PMD
	- Clock divider for STM and TPIU

Signed-off-by: Vaibhav Hiremath <hvaibhav@ti.com>
Acked-by: Paul Walmsley <paul@pwsan.com>
Cc: Tony Lindgren <tony@atomide.com>
Signed-off-by: Benoit Cousson <benoit.cousson@linaro.org>