rockchip: pinebook-pro: minor SPI flash fixes

Set a default offset for environment so it doesn't write it to
unexpected locations, drop unneeded mtd config option.

Signed-off-by: Peter Robinson <pbrobinson@gmail.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/configs/pinebook-pro-rk3399_defconfig b/configs/pinebook-pro-rk3399_defconfig
index 8ca1d07..aaa52c6 100644
--- a/configs/pinebook-pro-rk3399_defconfig
+++ b/configs/pinebook-pro-rk3399_defconfig
@@ -5,6 +5,7 @@
 CONFIG_SYS_TEXT_BASE=0x00200000
 CONFIG_NR_DRAM_BANKS=1
 CONFIG_ENV_SIZE=0x8000
+CONFIG_ENV_OFFSET=0x3F8000
 CONFIG_DEFAULT_DEVICE_TREE="rk3399-pinebook-pro"
 CONFIG_ROCKCHIP_RK3399=y
 CONFIG_TARGET_PINEBOOK_PRO_RK3399=y
@@ -22,7 +23,6 @@
 # CONFIG_SPL_RAW_IMAGE_SUPPORT is not set
 CONFIG_SPL_STACK_R=y
 CONFIG_SPL_STACK_R_MALLOC_SIMPLE_LEN=0x10000
-CONFIG_SPL_MTD_SUPPORT=y
 CONFIG_SPL_SPI_LOAD=y
 CONFIG_TPL=y
 CONFIG_CMD_BOOTZ=y