msm: tspp: remove msm_tspp_platform_data structure

TSPP clock names will not change for current platforms, so there
is no need to have them as parameters in the device tree node.
Moreover, upcoming platforms will use the generic device tree clocks
properties instead.
Removed cell-index property as well since there will always be one
instance of TSPP.

Change-Id: I504dfe8c8db87ee993411b068acf5b08ced34600
Signed-off-by: Gilad Broner <gbroner@codeaurora.org>