omap2 clock: remove fixed rate from mdm_osc_ck

omap2 clock: remove fixed rate from mdm_osc_ck

mdm_osc_ck has a preinitialized rate and is marked as RATE_FIXED, but rather
than using omap2_propagate_rate() as its recalc function, which accounts
for RATE_FIXED clocks, it uses omap2_followparent_recalc(), which sets the
rate to the parent clock's rate.  After reviewing the 2430 TRM, fix this
inconsistency by removing the fixed rate declarations (TRM says that this
clock is 'typically' 26MHz).

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