am33xx: Update SYS_MALLOC_F_LEN to use 0x2000 as the default

A number of platforms here had already been increasing the size a bit,
so lets moving all of them up.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/Kconfig b/Kconfig
index ff92a38..429e5d3 100644
--- a/Kconfig
+++ b/Kconfig
@@ -252,7 +252,7 @@
 	default 0x600 if ARCH_ZYNQMP_R5 || ARCH_ZYNQMP
 	default 0x800 if ARCH_ZYNQ || ROCKCHIP_RK3128 || ROCKCHIP_RK3188 || \
 			 ROCKCHIP_RK322X || X86
-	default 0x1000 if AM33XX || ARCH_MESON || ARCH_BMIPS || ARCH_MTMIPS
+	default 0x1000 if ARCH_MESON || ARCH_BMIPS || ARCH_MTMIPS
 	default 0x1800 if ARCH_TEGRA
 	default 0x4000 if SANDBOX || RISCV || ARCH_APPLE || ROCKCHIP_RK3368 || \
 			  ROCKCHIP_RK3399