OMAP3 clock: remove unnecessary duplicate of dpll4_m2_ck, added for 36xx

Commit 678bc9a2 split dpll4_m2_ck,
creating a 34xx and a 36xx variant, to handle the additional 16
divider steps provided on the 36xx.  This in turn required dynamic
rewriting of the clock tree during initialization, which is
undesirable.  All this seems to be unnecessary, though, since the
additional 16 divider steps can simply be marked with RATE_IN_36XX.
This patch does so and re-merges the affected structures.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Vishwanath Sripathy <vishwanath.bs@ti.com>