omap2 clock: move SDRC-related code from clock.c to memory.c

The clock framework contains two functions, omap2_dll_force_needed()
and omap2_reprogram_sdrc(), which are SDRC code, not really clock
code.  So, move these functions to memory.c.

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