ARM: uniphier: add DRAM init code for ProXstream2/PH1-LD6b

As mentioned in the log of commit 019df879a93e2 (ARM: uniphier: add
ProXstream2 and PH1-LD6b support), the DRAM init code was missing
for a long time.  Finally, here it is.  SPL works now.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/arch/arm/mach-uniphier/init.h b/arch/arm/mach-uniphier/init.h
index 27ae27d..0a47e70 100644
--- a/arch/arm/mach-uniphier/init.h
+++ b/arch/arm/mach-uniphier/init.h
@@ -80,6 +80,7 @@
 int ph1_ld4_umc_init(const struct uniphier_board_data *bd);
 int ph1_pro4_umc_init(const struct uniphier_board_data *bd);
 int ph1_sld8_umc_init(const struct uniphier_board_data *bd);
+int proxstream2_umc_init(const struct uniphier_board_data *bd);
 
 void ph1_sld3_pin_init(void);
 void ph1_ld4_pin_init(void);