configs/*imxrt10*: SYS_MALLOC_LEN is too large

1M of heap is more than internal ram making booting without SDRAM not
possible now it is 256k

Signed-off-by: Jesse Taube <Mr.Bossman075@gmail.com>
diff --git a/configs/imxrt1050-evk_defconfig b/configs/imxrt1050-evk_defconfig
index 118e717..7193e93 100644
--- a/configs/imxrt1050-evk_defconfig
+++ b/configs/imxrt1050-evk_defconfig
@@ -3,7 +3,7 @@
 # CONFIG_SPL_SYS_DCACHE_OFF is not set
 CONFIG_ARCH_IMXRT=y
 CONFIG_SYS_TEXT_BASE=0x80002000
-CONFIG_SYS_MALLOC_LEN=0x100000
+CONFIG_SYS_MALLOC_LEN=0x40000
 CONFIG_SYS_MALLOC_F_LEN=0x8000
 CONFIG_SPL_GPIO=y
 CONFIG_SPL_LIBCOMMON_SUPPORT=y