rockchip: Use pwrseq for MMC start-up on jerry

This is defined in the device tree in Linux. Copy over the settings so that
this can be used instead of hard-coding the reset line.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/chromebook_jerry_defconfig b/configs/chromebook_jerry_defconfig
index 39cd9d6..456b6ea 100644
--- a/configs/chromebook_jerry_defconfig
+++ b/configs/chromebook_jerry_defconfig
@@ -23,6 +23,7 @@
 CONFIG_LED=y
 CONFIG_SPL_LED=y
 CONFIG_LED_GPIO=y
+CONFIG_PWRSEQ=y
 CONFIG_RESET=y
 CONFIG_DM_MMC=y
 CONFIG_ROCKCHIP_DWMMC=y