board: tegra30: switch to button cmd

Use recently added ability to assign commands to buttons via env.

Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>
diff --git a/configs/transformer_t30_defconfig b/configs/transformer_t30_defconfig
index 992625a..11a552d 100644
--- a/configs/transformer_t30_defconfig
+++ b/configs/transformer_t30_defconfig
@@ -14,12 +14,13 @@
 CONFIG_TARGET_TRANSFORMER_T30=y
 CONFIG_CMD_EBTUPDATE=y
 CONFIG_SYS_LOAD_ADDR=0x82000000
+CONFIG_BUTTON_CMD=y
 CONFIG_BOOTDELAY=0
 CONFIG_AUTOBOOT_KEYED=y
 CONFIG_AUTOBOOT_KEYED_CTRLC=y
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_OF_SYSTEM_SETUP=y
-CONFIG_BOOTCOMMAND="setenv skip_boot 0; setenv gpio_button 150; if run check_button; then poweroff; fi; setenv gpio_button 131; if run check_button; then bootmenu; fi; if test ${skip_boot} -eq 1; then; else setenv boot_targets usb mmc1 mmc0; bootflow scan; poweroff; fi"
+CONFIG_BOOTCOMMAND="setenv boot_targets usb mmc1 mmc0; bootflow scan; poweroff"
 CONFIG_SYS_PBSIZE=2084
 CONFIG_SPL_FOOTPRINT_LIMIT=y
 CONFIG_SPL_MAX_FOOTPRINT=0x8000