CBMEM: Do not use get_top_of_ram() with DYNAMIC_CBMEM

The name was always obscure and confusing. Instead define cbmem_top()
directly in the chipset code for x86 like on ARMs.

TODO: Check TSEG alignment, it used for MTRR programming.

Change-Id: Ibbe5f05ab9c7d87d09caa673766cd17d192cd045
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/7888
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@google.com>

src/soc/intel/baytrail/memmap.c

@@ -22,12 +22,12 @@
 #include <baytrail/iosf.h>
 #include <baytrail/smm.h>
 
-void *smm_region_start(void)
+uintptr_t smm_region_start(void)
 {
-	return (void *)(iosf_bunit_read(BUNIT_SMRRL) << 20);
+	return (iosf_bunit_read(BUNIT_SMRRL) << 20);
 }
 
-unsigned long get_top_of_ram(void)
+void *cbmem_top(void)
 {
-	return (unsigned long)smm_region_start();
+	return (void *) smm_region_start();
 }