rockchip: rk3288-firefly: sync sdmmc pinctrl from mainline

The rk3288-firefly board have different setting for sdmmc
io, sync then from kernel mainline:
6fbc7275c7a9 Linux 5.2-rc7

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/arch/arm/dts/rk3288-firefly-u-boot.dtsi b/arch/arm/dts/rk3288-firefly-u-boot.dtsi
index 2efb309..8b9c383 100644
--- a/arch/arm/dts/rk3288-firefly-u-boot.dtsi
+++ b/arch/arm/dts/rk3288-firefly-u-boot.dtsi
@@ -29,11 +29,7 @@
 	u-boot,dm-pre-reloc;
 };
 
-&pcfg_pull_none_drv_8ma {
-	u-boot,dm-spl;
-};
-
-&pcfg_pull_up_drv_8ma {
+&pcfg_pull_up_drv_12ma {
 	u-boot,dm-spl;
 };