arm: lpc32xx: switch SPL builds to driver model

For NXP LPC32xx boards the change enables SPL_DM option, this allows
to use any driver model UART driver in SPL images, hence a restriction
on HSUART in SPL image is removed and well as definitions for non-DM
NS16550 driver, its DM version is used instead.

Because SPL_DM requires malloc(), enable CONFIG_SPL_SYS_MALLOC_SIMPLE
for LPC32xx boards.

The change adds about 5KB to the resulting SPL image (for devkit3250
board SPL image is increased from 10672 to 15608 bytes).

Signed-off-by: Vladimir Zapolskiy <vz@mleia.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/devkit3250_defconfig b/configs/devkit3250_defconfig
index 0abb8e0..ddf09fe 100644
--- a/configs/devkit3250_defconfig
+++ b/configs/devkit3250_defconfig
@@ -1,5 +1,7 @@
 CONFIG_ARM=y
 CONFIG_TARGET_DEVKIT3250=y
+CONFIG_SPL_SYS_MALLOC_SIMPLE=y
+CONFIG_SPL_DM=y
 CONFIG_DM_SERIAL=y
 CONFIG_DM_GPIO=y
 CONFIG_SPL=y