msm: clock-8x60: Map ppss_p_clk to the msm_dsps device

ppss_p_clk is used by the msm_dsps device, so mark it as such. Also
change the string name of the clock to "iface_clk" to match the naming
convention used for other clocks.

Change-Id: I035e6832a346561a999b6ea791754feb709a3bca
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>