2430 clock: remove redundant iva2_1_fck

iva2_1_fck, the 2430 DSP functional clock, is the same clock (from the
software's perspective) as dsp_fck - same registers, same bits, same
rates.  So, get rid of iva2_1_fck, and switch iva2_1_ick to take its
clock from dsp_fck instead, per the TRM.  Mark dsp_fck as existing on
all 24xx chips, not just 2420.  These changes resolve the "clock:
Could not find parent clock iva2_1_fck in clksel array of clock
iva2_1_ick" message that appears on boot.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>