powerpc: Move CONFIG_SYS_DDR_SIZE to CONFIG_SYS_SDRAM_SIZE

We have a number of CONFIG_SYS_xxx_SIZE options to describe the amount
main memory available.  Rework CONFIG_SYS_DDR_SIZE, which described a
size in number of MiB to use CONFIG_SYS_SDRAM_SIZE which is most often
used as a number of bytes.  Use shifts of this option when required.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/board/ids/ids8313/ids8313.c b/board/ids/ids8313/ids8313.c
index 45c77a2..48aea71 100644
--- a/board/ids/ids8313/ids8313.c
+++ b/board/ids/ids8313/ids8313.c
@@ -56,7 +56,7 @@
 int fixed_sdram(unsigned long config)
 {
 	immap_t *im = (immap_t *)CONFIG_SYS_IMMR;
-	u32 msize = CONFIG_SYS_DDR_SIZE << 20;
+	u32 msize = CONFIG_SYS_SDRAM_SIZE;
 
 #ifndef CONFIG_SYS_RAMBOOT
 	u32 msize_log2 = __ilog2(msize);
@@ -109,7 +109,7 @@
 
 static int setup_sdram(void)
 {
-	u32 msize = CONFIG_SYS_DDR_SIZE << 20;
+	u32 msize = CONFIG_SYS_SDRAM_SIZE;
 	long int size_01, size_02;
 
 	size_01 = fixed_sdram(CONFIG_SYS_DDR_CONFIG);