ARM: UniPhier: enable Driver Model and UART on SPL

Enable CONFIG_SPL_DM and CONFIG_SPL_SERIAL_SUPPORT, which provide
Driver Model UART support on SPL.

CONFIG_SYS_SPL_MALLOC_{START,SIZE} should be dropped because simple
malloc is preferred on SPL.  Dlmalloc requires some static variables
on .data section that is not available yet for NOR boot mode etc.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/configs/ph1_ld4_defconfig b/configs/ph1_ld4_defconfig
index 292f2ca..aa1805b 100644
--- a/configs/ph1_ld4_defconfig
+++ b/configs/ph1_ld4_defconfig
@@ -2,6 +2,7 @@
 CONFIG_ARCH_UNIPHIER=y
 CONFIG_DM=y
 CONFIG_DM_SERIAL=y
+CONFIG_SPL_DM=y
 CONFIG_DM_I2C=y
 CONFIG_MACH_PH1_LD4=y
 CONFIG_PFC_MICRO_SUPPORT_CARD=y