Kconfig: enlarge CONFIG_SYS_MALLOC_F_LEN

"alloc space exhausted" happens in very early stage, which could be seen
with DEBUG_UART options enabled and leeds to an non-functional board.

kontron_pitx_imx8m:
CONFIG_DEBUG_UART_BASE=0x30880000   # for serial3
CONFIG_DEBUG_UART_CLOCK=24000000

imx8mqevk:
CONFIG_DEBUG_UART_BASE=0x30860000      # for uart1
CONFIG_DEBUG_UART_CLOCK=24000000

It is because CONFIG_SYS_MALLOC_F_LEN is too small and still leave
CONFIG_SPL_SYS_MALLOC_F_LEN as 0x2000.

Reported-by: Heiko Thiery <heiko.thiery@gmail.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Heiko Thiery <heiko.thiery@gmail.com>
Tested-by: Heiko Thiery <heiko.thiery@gmail.com>
Reviewed-by: Fabio Estevam <festevam@denx.de>
diff --git a/Kconfig b/Kconfig
index 991b260..c8c2255 100644
--- a/Kconfig
+++ b/Kconfig
@@ -299,7 +299,7 @@
 	default 0x4000 if SANDBOX || RISCV || ARCH_APPLE || ROCKCHIP_RK3368 || \
 			  ROCKCHIP_RK3399
 	default 0x8000 if RCAR_GEN3
-	default 0x10000 if ARCH_IMX8 || (ARCH_IMX8M && !IMX8MQ)
+	default 0x10000 if ARCH_IMX8 || ARCH_IMX8M
 	default 0x2000
 	help
 	  Before relocation, memory is very limited on many platforms. Still,
@@ -325,6 +325,7 @@
 	depends on SYS_MALLOC_F && SPL
 	default 0 if !SPL_FRAMEWORK
 	default 0x2800 if RCAR_GEN3
+	default 0x2000 if IMX8MQ
 	default SYS_MALLOC_F_LEN
 	help
 	  In SPL memory is very limited on many platforms. Still,