Exynos5250: Get DDR3 working by changing what is compiled and add a function

This is a minor set of changes to get DDR3 going.

Move compilation of DDR3 startup to the romstage. Fix a prototype that
was missing a void. Remove a function that is overly flexible, and
even though it is overly flexible only actually can handle one type of
RAM. Mainboards only support one type of DRAM, so create a function
to explicitly initialize the type of DDR we have -- DDR3.

With these changes, and the previous changes, google snow is ready to run
the ramstage.

Change-Id: I37e0ab0d2dbc1dd121fb175386a46bc2fb1285e5
Signed-off-by: Ronald G. Minnich <rminnich@gmail.com>
Reviewed-on: http://review.coreboot.org/2224
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: David Hendricks <dhendrix@chromium.org>

src/cpu/samsung/exynos5250/clock_init.c

@@ -744,7 +744,7 @@ struct mem_timings *clock_get_mem_timings(void)
 	return NULL;
 }
 
-void system_clock_init()
+void system_clock_init(void)
 {
 	struct exynos5_clock *clk = (struct exynos5_clock *)EXYNOS5_CLOCK_BASE;
 	struct exynos5_mct_regs *mct_regs =