arm: kirkwood: sheevaplug: reduce u-boot image size

Sheevaplug board has 512K CONFIG_BOARD_SIZE_LIMIT. Recently, DM_SERIAL has
pushed the image size a few hundred bytes over that limit. So explicitly
deselect some configs that are unrelated to this board
(and gain back a bit over 2K).

Signed-off-by: Tony Dinh <mibodhi@gmail.com>
diff --git a/configs/sheevaplug_defconfig b/configs/sheevaplug_defconfig
index cb38a3f..40ab16d 100644
--- a/configs/sheevaplug_defconfig
+++ b/configs/sheevaplug_defconfig
@@ -26,6 +26,11 @@
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_MAXARGS=32
 CONFIG_CMD_BOOTZ=y
+# CONFIG_BOOTM_PLAN9 is not set
+# CONFIG_BOOTM_RTEMS is not set
+# CONFIG_BOOTM_VXWORKS is not set
+# CONFIG_CMD_IMI is not set
+# CONFIG_CMD_XIMG is not set
 # CONFIG_CMD_FLASH is not set
 CONFIG_CMD_MMC=y
 CONFIG_CMD_NAND=y