board: transformer-t30: convert ASUS Transformers to use DM PMIC

Since required drivers were merged, we can safely clean up the
board and switch to DM based driver with device tree support.

Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>
diff --git a/board/asus/transformer-t30/configs/tf600t.config b/board/asus/transformer-t30/configs/tf600t.config
index 18ab4fb..e40d0fd 100644
--- a/board/asus/transformer-t30/configs/tf600t.config
+++ b/board/asus/transformer-t30/configs/tf600t.config
@@ -1,4 +1,4 @@
 CONFIG_DEFAULT_DEVICE_TREE="tegra30-asus-tf600t"
-CONFIG_TRANSFORMER_SPI_BOOT=y
 CONFIG_BOOTCOMMAND="setenv gpio_button 222; if run check_button; then poweroff; fi; setenv gpio_button 132; if run check_button; then echo Starting SPI flash update ...; run update_spi; fi; run bootcmd_usb0; run bootcmd_mmc1; run bootcmd_mmc0; poweroff;"
+CONFIG_SPI_FLASH_WINBOND=y
 CONFIG_USB_GADGET_PRODUCT_NUM=0x4d00