ARM: keystone2: use detected ddr3a size

Because KS2 u-boot works in 32 bit address space the existing ram_size
global data field cannot be used. The maximum, which the get_ram_size()
can detect is 2GB only. The ft_board_setup() needs the actual ddr3 size
to fix up dtb.

This commit introduces the ddr3_get_size() which uses SPD data to
calculate the ddr3 size. This function replaces the "ddr3_size"
environment variable, which was used to get the SODIMM size.

For platforms, which don't have SODIMM with SPD and ddr3 is populated to
a board a simple ddr3_get_size function that returns ddr3 size has to be
implemented. See hardware-k2l.h

Signed-off-by: Vitaly Andrianov <vitalya@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/arm/mach-keystone/include/mach/ddr3.h b/arch/arm/mach-keystone/include/mach/ddr3.h
index 68d3cb4..5feffe8 100644
--- a/arch/arm/mach-keystone/include/mach/ddr3.h
+++ b/arch/arm/mach-keystone/include/mach/ddr3.h
@@ -66,5 +66,6 @@
 void ddr3_enable_ecc(u32 base, int test);
 void ddr3_init_ddrphy(u32 base, struct ddr3_phy_config *phy_cfg);
 void ddr3_init_ddremif(u32 base, struct ddr3_emif_config *emif_cfg);
+int ddr3_get_size(void);
 
 #endif