Kconfig: Enlarge default SYS_MALLOC_F_LEN for AM33XX

Since commit 8e14ba7b ("gpio: omap_gpio: Add DM_FLAG_PRE_RELOC
flag") omap GPIO gets bound before relocation.  Unfortunately due to
this, on at least the beaglebone black, the pre-relocation memory pool
gets exhausted before probing the serial port. This then causes u-boot
to panic as CONFIG_REQUIRE_SERIAL_CONSOLE is set...

Resolve this by resizing the default size of the pre-relocation malloc
pool for AM335X platforms.

Signed-off-by: Sjoerd Simons <sjoerd.simons@collabora.co.uk>

Kconfig

@@ -132,6 +132,7 @@ config SYS_MALLOC_F
 config SYS_MALLOC_F_LEN
 	hex "Size of malloc() pool before relocation"
 	depends on SYS_MALLOC_F
+	default 0x1000 if AM33XX
 	default 0x400
 	help
 	  Before relocation, memory is very limited on many platforms. Still,